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Document and Entity Information	12 Months Ended
Document and Entity Information	Dec. 31, 2017 shares
Entity Registrant Name	WEIBO Corp
Entity Central Index Key	0001595761
Document Type	20-F
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Class A ordinary shares
Entity Common Stock, Shares Outstanding	120,926,916
Class B ordinary shares
Entity Common Stock, Shares Outstanding	101,778,958
Ordinary Shares
Entity Common Stock, Shares Outstanding	222,705,874

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 1,000,953	$ 364,766
Short-term investments	791,730	31,188
Accounts receivable due	170,100	116,054
Prepaid expenses and other current assets	69,233	66,664
Amount due from SINA	16,356	18,565
Total current assets	2,048,372	597,237
Property and equipment, net	33,793	22,816
Intangible assets, net	517	1,100
Goodwill	13,420	10,266
Long-term investments	452,337	399,933
Other assets	13,380	5,592
Total assets	2,561,819	1,036,944
Current liabilities (including amounts of the consolidated VIE without recourse to the primary beneficiaries of $137,256 and $217,602 as of December 31, 2016 and 2017, respectively.)
Accounts payable	134,950	48,997
Accrued and other liabilities	268,615	180,142
Deferred revenues	81,311	48,964
Total current liabilities	484,876	278,103
Long-term liabilities
Convertible debt	879,983
Long-term deferred revenues	286	666
Deferred tax liability	1,880	817
Total long-term liabilities	882,149	1,483
Total liabilities	1,367,025	279,586
Commitments and contingencies (Note 16)
Shareholders' equity:
Ordinary shares: $0.00025 par value; 2,400,000 and 2,400,000 shares (including 1,800,000 Class A ordinary shares, 200,000 Class B ordinary shares and 400,000 shares to be designated) authorized; 218,076 and 222,706 shares (including 120,927 Class A ordinary shares and 101,779 Class B ordinary shares) issued and outstanding as of December 31, 2016 and 2017, respectively.	56	55
Additional paid-in capital	1,030,048	979,805
Accumulated other comprehensive income (loss)	9,534	(26,994)
Retained earnings (Accumulated deficit)	152,949	(199,641)
Total Weibo shareholders' equity	1,192,587	753,225
Non-controlling interests	2,207	4,133
Total shareholders' equity	1,194,794	757,358
Total liabilities and shareholders' equity	2,561,819	1,036,944
Third parties
Current assets:
Accounts receivable due	97,572	61,655
Alibaba
Current assets:
Accounts receivable due	42,832	24,293
Other related parties
Current assets:
Accounts receivable due	$ 29,696	$ 30,106

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 8,114	$ 6,529
Current liabilities	$ 484,876	$ 278,103
Ordinary shares, par value (in dollars per share)	$ 0.00025	$ 0.00025
Ordinary shares, shares authorized	2,400,000	2,400,000
Ordinary shares, shares issued	222,706	218,076
Ordinary shares, shares outstanding	222,706	218,076
Class A ordinary shares
Ordinary shares, shares authorized	1,800,000	1,800,000
Ordinary shares, shares issued	120,927
Ordinary shares, shares outstanding	120,927
Class B ordinary shares
Ordinary shares, shares authorized	200,000	200,000
Ordinary shares, shares issued	101,779
Ordinary shares, shares outstanding	101,779
Ordinary shares to be designated
Ordinary shares, shares authorized	400,000	400,000
Consolidated VIEs without recourse to the primary beneficiaries
Current liabilities	$ 217,602	$ 137,256
Alibaba
Allowance for doubtful accounts	0	0
Other related parties
Allowance for doubtful accounts	0	1,483
Third parties
Allowance for doubtful accounts	$ 8,114	$ 5,046

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Advertising and marketing revenues
Third parties	$ 780,545	$ 428,275	$ 207,657
Total advertising and marketing revenues	996,745	570,982	402,415
Value-added services revenues	153,309	84,818	75,476
Total revenues	1,150,054	655,800	477,891
Costs and Expenses
Cost of revenues	231,255	171,231	141,960
Sales and marketing	275,537	148,283	126,059
Product development	193,393	154,088	143,444
General and administrative	42,315	41,218	28,925
Total costs and expenses	742,500	514,820	440,388
Income from operations	407,554	140,980	37,503
Income (loss) from equity method investments	1,030	(130)	(6)
Realized gain from investments	14	534	944
Investment related impairment	(4,747)	(40,161)	(8,005)
Interest and other income, net	13,260	8,757	6,344
Income before income tax expenses	417,111	109,980	36,780
Provision of income taxes	66,746	4,316	2,591
Net income	350,365	105,664	34,189
Less: Net loss attributable to non-controlling interests	(2,225)	(2,363)	(556)
Net income attributable to Weibo	352,590	108,027	34,745
Other comprehensive income (loss)
Currency translation adjustments (net of tax of nil, nil, and nil for 2015, 2016 and 2017, respectively)	37,822	(18,898)	(7,874)
Available-for-Sale securities
Change in unrealized loss from available-for-sale securities (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	(995)	(2,557)	(198)
Reclassification adjustment for net loss included in net income (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)		4,822
Net change, net of tax	(995)	2,265	(198)
Total comprehensive income	387,192	89,031	26,117
Less: Comprehensive loss attributable to non-controlling interests	(1,926)	(2,637)	(829)
Comprehensive income attributable to Weibo	$ 389,118	$ 91,668	$ 26,946
Shares used in computing net income per share attributable to Weibo:
Basic (in shares)	220,555	214,745	208,163
Diluted (in shares)	225,363	222,859	217,918
Income per share:
Basic (in dollars per share)	$ 1.60	$ 0.50	$ 0.17
Diluted (in dollars per share)	$ 1.56	$ 0.48	$ 0.16
Alibaba
Advertising and marketing revenues
Related party	$ 84,688	$ 57,908	$ 143,650
SINA and other related parties
Advertising and marketing revenues
Related party	$ 131,512	$ 84,799	$ 51,108

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Currency translation adjustments, tax	$ 0	$ 0	$ 0
Change in unrealized loss from available-for-sale securities, tax	0	0	0
Reclassification adjustment for net loss included in net income, tax	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Ordinary Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Non-controlling Interests	Total
Balance at Dec. 31, 2014	$ 51	$ 904,402	$ (2,836)	$ (342,413)	$ 8,186	$ 567,390
Balance (in shares) at Dec. 31, 2014	203,658
Increase (Decrease) in Shareholders' Equity
Issuance of ordinary shares pursuant to stock plan	$ 2	8,121				8,123
Issuance of ordinary shares pursuant to stock plan (in shares)	8,519
Non-cash stock-based compensation		26,399				26,399
Net income (loss)				34,745	(556)	34,189
Currency translation adjustments			(7,601)		(273)	(7,874)
Net change in other comprehensive loss from available-for-sale securities			(198)			(198)
Balance at Dec. 31, 2015	$ 53	938,922	(10,635)	(307,668)	7,357	628,029
Balance (in shares) at Dec. 31, 2015	212,177
Increase (Decrease) in Shareholders' Equity
Issuance of ordinary shares pursuant to stock plan	$ 2	3,981				3,983
Issuance of ordinary shares pursuant to stock plan (in shares)	5,899
Non-cash stock-based compensation		36,902				36,902
Sale (Purchase) of subsidiaries' shares to (from) non-controlling shareholders, net					(587)	(587)
Net income (loss)				108,027	(2,363)	105,664
Currency translation adjustments			(18,624)		(274)	(18,898)
Net change in other comprehensive loss from available-for-sale securities			2,265			2,265
Balance at Dec. 31, 2016	$ 55	979,805	(26,994)	(199,641)	4,133	$ 757,358
Balance (in shares) at Dec. 31, 2016	218,076					218,076
Increase (Decrease) in Shareholders' Equity
Issuance of ordinary shares pursuant to stock plan	$ 1	2,206				$ 2,207
Issuance of ordinary shares pursuant to stock plan (in shares)	4,630
Non-cash stock-based compensation		48,037				48,037
Net income (loss)				352,590	(2,225)	350,365
Currency translation adjustments			37,523		299	37,822
Net change in other comprehensive loss from available-for-sale securities			(995)			(995)
Balance at Dec. 31, 2017	$ 56	$ 1,030,048	$ 9,534	$ 152,949	$ 2,207	$ 1,194,794
Balance (in shares) at Dec. 31, 2017	222,706					222,706

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 350,365	$ 105,664	$ 34,189
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,328	13,982	20,950
Stock-based compensation	48,037	36,902	26,399
Provision (reversal) for allowance for doubtful accounts	5,478	7,787	(368)
Deferred income tax benefits	(1,503)	(4,630)	(977)
(Income) Loss from equity method investments	(1,030)	130	6
Dividend received from equity method investments	267
Gain on sale of investments	(14)	(328)	(608)
Investment related impairment	4,747	40,161	8,005
(Gain) Loss on disposal of property and equipment	(85)	191	184
Amortization of convertible debt issuance cost	690
Changes in assets and liabilities, net of acquisition:
Prepaid expenses and other current assets	(28,050)	(19,527)	470
Other assets	(649)	1,134	713
Accounts payable	84,444	8,915	16,099
Accrued and other liabilities	88,474	68,102	46,271
Deferred revenues	31,967	9,492	17,753
Net cash provided by operating activities	539,151	236,244	181,971
Cash flows from investing activities:
Purchases of short-term investments	(1,439,558)	(314,363)	(149,374)
Maturities of short-term investments	696,245	373,805	216,615
Investment and prepayment in long-term investments	(54,640)	(155,122)	(268,758)
Proceeds from disposal/refund of long-term investments	2,458	12,188	6,090
Proceeds from disposal of property and equipment	107
Purchases of property and equipment	(20,454)	(13,253)	(10,858)
Cash paid for business acquisition, net of cash acquired	(2,298)		(22,025)
Net cash used in investing activities	(815,422)	(96,745)	(228,310)
Cash flows from financing activities:
Proceeds from employee options exercised	2,285	4,183	7,822
Proceeds from convertible notes, net of debt issuance costs	879,293
Payments to non-controlling shareholders		(1,148)
Net cash provided by financing activities	883,578	3,035	4,959
Effect of exchange rate changes on cash and cash equivalents	28,880	(15,208)	(6,045)
Net increase (decrease) in cash and cash equivalents	636,187	127,326	(47,425)
Cash and cash equivalents at the beginning of the year	364,766	237,440	284,865
Cash and cash equivalents at the end of the year	1,000,953	364,766	237,440
Supplemental disclosure of cash flow information
Cash paid for income tax	(8,168)	(3,386)	(311)
Supplemental schedule of non-cash investing and financing activities
Property and equipment in accounts payable	3,667	2,158	2,532
Uncollected proceeds from sale of subsidiary's shares to non-controlling shareholders		561
Third parties
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from third parties	(41,395)	(33,109)	4,988
Alibaba
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from Alibaba	(18,539)	29,759	10,673
Other related parties
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from other related parties	410	2,372	(15,313)
SINA
Changes in assets and liabilities, net of acquisition:
Amount due to (from) SINA	209	$ (30,753)	12,537
Cash flows from investing activities:
Loan to SINA	(59,534)
Repayment of loan by SINA	62,252
Cash flows from financing activities:
Loan from SINA	62,000
Repayment of loan from SINA	(60,000)		$ (2,863)
Supplemental disclosure of cash flow information
Cash paid for interest expenses on matching loan from SINA	$ (1,537)

Operations and reorganization

12 Months Ended

Dec. 31, 2017

Operations and reorganization

Operations and reorganization

1. Operations and reorganization

Weibo Corporation (“Weibo” or the “Company”) is a leading social media for people to create, share and discover Chinese-language content. It provides an unprecedented and simple way for people and organizations to publicly express themselves in real time, interact with others on a massive global platform and stay connected with the world. As a microcosm of the Chinese society and a cultural phenomenon in China, Weibo allows people to be heard publicly and exposed to the rich ideas, cultures and experiences of the broader world. Media outlets use Weibo as a source of news and a distribution channel for their headline news. Government agencies and officials use Weibo as an official communication channel for disseminating information timely and gauging public opinion to improve public services. Charities use Weibo to make the world a better place by launching charitable projects, seeking donations and volunteers and leveraging celebrities and organizations on Weibo to amplify their impact to society. Weibo generates its revenues mostly from advertising and marketing services, as well as from value-added services, including game-related services, VIP membership and data licensing.

Incorporated in the Cayman Islands, Weibo Corporation is a controlled subsidiary of Sina Corporation (the “Parent” or “SINA”). In April 2014, the Company completed an initial public offering (the “IPO”) with the new issuance of 19,320,000 Class A ordinary shares and received $306.5 million in net proceeds. Immediately prior to the completion of the IPO, all the ordinary shares held by SINA was converted into an equal number of the Class B ordinary shares, all the ordinary shares held by other shareholders was converted into an equal number of the Class A ordinary shares, and all of its outstanding preferred shares were automatically converted into 30,046,154 Class A ordinary shares. The call option held by a subsidiary of Alibaba Group was exercised to purchase 29,990,778 Class A ordinary shares from SINA and the Company. Each Class A ordinary share is entitled to one vote per share and each Class B ordinary share is entitled to three votes per share. Each Class B ordinary share can be converted into one Class A ordinary share at any time, while Class A ordinary shares cannot be converted into Class B ordinary shares.

Reorganization

The Weibo business was founded by SINA, its parent, in 2009. Prior to the establishment of the Company, the operation of Weibo business was carried out by various subsidiaries and variable interest entities (“VIE”) of SINA (the “Predecessor Operations”). After its establishment, the Company gradually completed the reorganization steps as described below (the “Reorganization”).

Establishment of Weibo Corporation. Weibo Corporation, an exempted company with limited liability, is the holding company for the Weibo business. Weibo HK is a wholly owned subsidiary of Weibo, and Weibo Technology, a wholly foreign-owned enterprise, (“the WFOE”), is a subsidiary of Weibo HK. The Company’s VIE and VIE’s subsidiaries are controlled by the WFOE through a series of contractual agreements. Weibo Corporation, its subsidiaries, VIE and VIE’s subsidiaries together are referred to as “the Group.”

The following sets forth the Company’s major subsidiaries, VIE and VIE’s subsidiary:

Company	Date of Incorporation	Place of Incorporation	Percentage of Direct/ Indirect Economic Interest
Major Subsidiaries
Weibo Hong Kong Limited (“Weibo HK”)	July 19, 2010	Hong Kong	100	%

Weibo Internet Technology (China) Co., Ltd. (“Weibo Technology” or “the WFOE”)	October 11, 2010	PRC	100	%

Major VIE and VIE’s subsidiary
Beijing Weimeng Technology Co., Ltd (“Weimeng”)	August 9, 2010	PRC	100	%

Beijing Weibo Interactive Internet Technology Co., Ltd. (‘‘Weibo Interactive’’)	Acquired in May 2013	PRC	100	%

Transfer of Equity Interest in Weibo Funds. SINA held a 55% and 85% equity interest in two limited liability partnerships, (“Weibo Funds’’), since 2011 and 2013, respectively, and had control over the operations and assets of the Weibo Funds, which engage in the investment of high-tech startups related to the Weibo business. On June 30, 2015, SINA transferred its equity interest in the Weibo Funds to the Group for a consideration of $22.0 million, and the Group accounted for such transaction as a business combination between entities under common control (Note 5). The Group’s consolidated financial statements have been retrospectively adjusted to reflect the transfer from the first day SINA took control.

The amounts recognized in the Group’s consolidated financial statements reflect the assets, liabilities, and net equity of the Weibo Funds at SINA’s historical carrying value. A consideration of $22.0 million payable to SINA was recognized when the transfer became legally effective in June 2015.

Intellectual Property License Agreement. The intellectual property license agreement was entered into by and between SINA and the Company in April 2013. Under this agreement, SINA granted the Company and its subsidiaries a perpetual, worldwide, royalty-free, fully paid-up, non-sublicensable, non-transferable, limited, exclusive license of certain trademarks and a non-exclusive license of certain other intellectual property owned by SINA to make, sell, offer to sell and distribute products, services and applications on a microblogging and social networking platform. The Company granted SINA and its affiliates a non-exclusive, perpetual, worldwide, non-sublicensable, non-transferable limited license of certain of the Company’s intellectual property to use, reproduce, modify, prepare derivative works of, perform, display or otherwise exploit such intellectual property. This agreement commenced on April 29, 2013 and will continue to be in effect unless terminated by SINA should the Company breach the terms as provided in the agreement.

Basis of Presentation for the Reorganization. Since the Group and the Predecessor Operations are under common control, the accompanying consolidated financial statements include the assets, liabilities, revenue, expenses and cash flows that were directly attributable to the Predecessor Operations for all periods presented. The assets and liabilities have been stated at historical carrying amounts. In addition, the accompanying consolidated financial statements have been prepared as if the current corporate structure, including the transfer of Weibo Funds in June 2015, had been in existence throughout the periods presented.

Accounts receivable amounts directly related to Weibo but for which SINA will receive payments and remit payments to the Group are included in the amount due from SINA. Liabilities directly related to Weibo but for which SINA will make payments and receive reimbursements from the Group are included in the amount due to SINA. Loan from SINA is presented under cash flow from financing activities, whereas loan to SINA is presented under investing activities in the consolidated statements of cash flows. Cash payment for billings from SINA for costs and expenses allocated is presented under operating activities in the consolidated statements of cash flows. The Group’s statements of comprehensive income consists all the related costs and expenses of the Weibo business, including allocation to the cost of revenues, sales and marketing expenses, product development expenses, and general and administrative expenses, which are incurred by SINA but related to the Weibo business. These allocations were based on proportional cost allocation by considering proportion of the revenues, infrastructure usage metrics and labor usage metrics, among other things, attributable to the Group and are made on a basis considered reasonable by management.

Total cost and expenses allocated from SINA were as follows:

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Cost of revenues	$	6,550	$	11,022	$	13,699
Sales and marketing	1,263		1,271		9,732
Product development	12,981		9,094		11,312
General and administrative	3,884		4,316		6,393

	$	24,678	$	25,703	$	41,136

However, while the expenses allocated to the Group for these items are not necessarily indicative of the expenses that would have been incurred if the Group had been a separate and independent entity, the Company does not believe that there is any significant difference between the nature and amount of these allocated expenses and the expenses that would have been incurred if the Group had been a separate and stand-alone entity.

Consolidation

The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries, VIEs, of which the Company is the primary beneficiary, and VIEs’ subsidiaries. All significant intercompany balances and transactions have been eliminated.

To comply with PRC laws and regulations, the Group provides a substantial amount of its services in China via the VIE, which holds critical operating licenses that enable the Group to do business in China. Most of the Group’s revenues, costs and net income in China were generated directly or indirectly through the VIE or the Predecessor Operations. The Company, through its subsidiary, has signed various agreements with the VIE to allow the transfer of economic benefits from the VIE to the Company. The Group has determined that it is the primary beneficiary of the VIE through Weibo Technology’s contractual arrangements with the VIE. Accordingly, the Company has consolidated the VIE’s results of operations and assets and liabilities in the Group’s financial statements pursuant to the United States Generally Accepted Accounting Principles (“US GAAP”) for all the periods presented.

Shareholders of the VIE are certain nominee shareholders from the Company or SINA. The capital for their investments in the VIE is funded by the Company and recorded as interest-free loans to these individuals. These loans were eliminated with the capital of the VIE during consolidation. Each shareholder of the VIE has agreed to transfer his equity interest in the VIE to Weibo Technology when permitted by PRC laws and regulations or to designees of the Company at any time for the amount of loans outstanding. All voting rights of the VIE, including without limitation the right to appoint all directors of the VIE, have been assigned to Weibo Technology. Weibo Technology has also entered into exclusive technical service agreements with the VIE under which Weibo Technology provides technical and other services to the VIE in exchange for substantially all net income of the VIE. In addition, the shareholders of the VIE have pledged their shares in the VIE as collateral for the non-payment of loans or for the technical and other services fees due to Weibo Technology. As of December 31, 2016 and 2017, the total amount of interest-free loans to the VIE’s shareholders was $9.4 million and $86.9 million, respectively and the aggregate accumulated loss of the VIE and VIE’s subsidiaries was $54.5 million and $33.3 million, respectively, which were included in the Group’s consolidated financial statements.

The following table sets forth the assets, liabilities, results of operations and cash flows of the VIE and VIE’s subsidiaries taken as a whole, which are included in the Group’s consolidated balance sheets and statements of comprehensive income:

	As of December 31,
	2016		2017
	(In thousands)
Cash, cash equivalents and short-term Investments	$	57,505	$	40,458
Accounts receivable	115,338		166,212
Property and equipment, net	357		146
Intangible assets	1,100		517
Goodwill	9,969		13,123
Prepayment for long-term investments	144		4,967
Long-term investments	49,195		74,935
Deferred tax assets	2,312		4,772
Amount due from SINA	12,163		4,677
Others	28,247		28,850

Total assets	$	276,330	$	338,657


Accounts payable	$	25,850	$	32,444
Accrued and other liabilities	64,879		114,239
Deferred revenues	38,313		54,651
Income tax payable	8,214		16,268
Amount due to the subsidiaries of the Group	171,460		57,639
Deferred tax liability	274		129

Total liabilities	$	308,990	$	275,370

	Year Ended December 31,
	2015			2016			2017
	(In thousands)
Net revenues	$	391,568		$	530,598		$	906,129
Net income (loss)	$	(10,572	)	$	(21,758	)	$	21,252

	Year Ended December 31,
	2015			2016			2017
	(In thousands)
Net cash provided by (used in) operating activities	$	158,290		$	(42,556	)	$	(66,972	)
Net cash used in investing activities	$	(39,965	)	$	(28,577	)	$	(34,720	)
Net cash provided by (used in) financing activities	$	—		$	(1,148	)	$	76,232

Net increase (decrease) in cash and cash equivalents	$	118,325		$	(72,281	)	$	(25,460	)

Under the contractual arrangements with the VIE, the Company has the power to direct activities of the VIE through Weibo Technology and can have assets transferred freely out of the VIE without restrictions. Therefore, the Company considers that there is no asset of the VIE that can only be used to settle obligations of the VIE and VIE’s subsidiaries, except for the registered capital and non-distributable reserve funds of the VIE and VIE’s subsidiaries, amounting to $56.2 million and $137.3 million as of December 31, 2016 and 2017, respectively. Since the VIE is incorporated as limited liability company under the PRC Company Law, creditors of the VIE do not have recourse to the general credit of the Company. There is currently no contractual arrangement that would require the Company to provide additional financial support to the VIE. As the Company is conducting certain businesses mainly through the VIE, the Company may provide such support on a discretionary basis in the future, which could expose the Company to a loss. The total amount of costs and expenses allocated from SINA to the VIE was $8.4 million, $12.3 million and $21.4 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Unrecognized revenue-producing assets held by the VIE include the Internet Content Provision License, the Online Culture Operating Permit, and the domain names of Weibo.com, Weibo.cn and Weibo.com.cn. Recognized revenue-producing assets held by the VIE include customer lists relating to game-related services, game platform technology and a non-compete agreement, which were acquired mostly through acquisitions. Unrecognized revenue-producing assets, including customer lists relating to advertising and marketing services, game-related services, VIP membership and data licensing, as well as trademarks, are also held by Weibo Technology.

The following is a summary of the VIE agreements:

Loan Agreements. The Company’s wholly owned subsidiary Weibo Technology has granted interest-free loans to each shareholder of the VIE with the sole purpose of providing funds necessary for capital injection into the VIE. The terms of the loans are for 10 years, and Weibo Technology has the right to, at its own discretion, shorten or extend the terms of the loans, if necessary. These loans were eliminated with the capital of the VIE during consolidation.

Share Transfer Agreements. Each shareholder of the VIE has granted Weibo Technology an option to purchase his shares in the VIE at a purchase price equal to the amount of the capital injection. Weibo Technology may exercise such option at any time until it has acquired all of the shares of the VIE, subject to applicable PRC laws. The option will be effective until the earlier of (i) the shareholders of the VIE and Weibo Technology have fully performed their obligations under this agreement, and (ii) the respective shareholders of the VIE and Weibo Technology agree to terminate the share transfer agreement in writing.

Loan Repayment Agreements. Each shareholder of the VIE has agreed with Weibo Technology that the interest-free loans under the loan agreements shall only be repaid through share transfer. Once the share transfers are completed, the purchase price for the share transfer will be set off against the loan repayment. These agreements will be effective until the earlier of (i) Weibo Technology and the shareholders of the VIE have fully performed their obligations under these agreements, and (ii) Weibo Technology and the shareholders of the VIE agree in writing to terminate these agreements.

Agreements on Authorization to Exercise Shareholder’s Voting Power. Each shareholder of the VIE has authorized Weibo Technology to exercise all his voting power as a shareholder of the VIE on all matters requiring shareholders’ approval under PRC laws and regulations and the articles of association of the VIE, including without limitation to the appointment of directors, transfer, mortgage or dispose of the VIE’s assets, transfer of any equity interest in the VIE, and merger, split, dissolution and liquidation of the VIE. The authorizations are irrevocable and will not expire until the VIE dissolves.

Share Pledge Agreements. Each shareholder of the VIE has pledged all of his shares in the VIE and all other rights relevant to the share rights to Weibo Technology, as a collateral security for his obligations to pay off all debts to Weibo Technology, under the loan agreement and for the payment obligations of the VIE under the trademark license agreement and the technical services agreement. In the event of default of any payment obligations, Weibo Technology will be entitled to certain rights, including transferring the pledged shares to itself and disposing the pledged shares through sale or auction. During the term of each agreement, Weibo Technology is entitled to receive all dividends and distributions paid on the pledged shares. The pledges will be effective until the earlier of (i) the third anniversary of the due date of the last guaranteed debt, (ii) the VIE and the shareholders of the VIE have fully performed their obligations under the above-referred agreements, and (iii) Weibo Technology unilaterally consents to terminate the respective share pledge agreement. As of the date of this annual report, the registration of such equity pledges is still in the process.

Exclusive Technical Services Agreement, Exclusive Sales Agency Agreement and Trademark License Agreement. The VIE has entered into an exclusive technical services agreement, an exclusive sales agency agreement and a trademark license agreement with Weibo Technology. Under the exclusive technical services agreement, Weibo Technology is engaged to provide technical services for the VIE’s online advertising and other related businesses. Under the exclusive sales agency agreement, the VIE has granted Weibo Technology the exclusive right to distribute, sell and provide agency services for all the products and services provided by the VIE. The term of the technical service agreement and the sales agency agreement will not expire until the VIE dissolves.

Due to its control over the VIE, Weibo Technology has the right to determine the service fee to be charged to the VIE under these agreements. By considering, among other things, the technical complexity of the service, the actual cost that may be incurred for providing such service, the operations of the VIE, applicable tax rates, planned capital expenditure and business strategies, Weibo Technology charged an amount of $232.4 million, $335.6 million and $618.1 million in service fees from the VIE under these agreements for the years ended December 31, 2015, 2016 and 2017, respectively, which was determined based on the actual cost incurred for providing such service and the cash position and operation of the VIE.

Under the trademark license agreement, Weibo Technology has granted the VIE trademark licenses to use its trademarks for specific areas, and the VIE is obligated to pay license fees to Weibo Technology. The term of the agreement is for one year and is automatically renewed provided that there is no objection from Weibo Technology.

The Company believes that the contractual arrangements among its subsidiary, VIE and VIE’s shareholders are in compliance with the current PRC laws and legally enforceable. However, uncertainties in the interpretation and enforcement of the PRC laws, regulations and policies could limit the Company’s ability to enforce these contractual arrangements. As a result, the Company may be unable to consolidate the VIE and VIE’s subsidiaries in the consolidated financial statements. The Company’s ability to control the VIE also depends on the authorization by the shareholders of the VIE to exercise voting rights on all matters requiring shareholder approval in the VIE. The Company believes that the agreements on authorization to exercise shareholder’s voting power are legally enforceable. In addition, if the legal structure and contractual arrangements with the VIE were found to be in violation of any future PRC laws and regulations, the Company may be subject to fines or other actions. The Company believes the possibility that it will no longer be able to control and consolidate the VIE as a result of the aforementioned risks and uncertainties are remote.

Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Significant Accounting Policies

Significant Accounting Policies

2. Significant Accounting Policies

Basis of presentation

The preparation of the Group’s consolidated financial statements is in conformity with US GAAP. The consolidated financial statements include the accounts of Weibo, its wholly owned subsidiaries, VIE, and VIE’s subsidiaries. All significant intercompany balances and transactions have been eliminated.

Use of estimates

Conformity with US GAAP requires the use of estimates and judgments that affect the reported amounts in the consolidated financial statements and accompanying notes. These estimates form the basis for judgments the management makes about the carrying values of the assets and liabilities, which are not readily apparent from other sources. GAAP requires making estimates and judgments in several areas, including, but not limited to, the basis of consolidation, revenue recognition, fair value accounting, income taxes, goodwill and other long-lived assets, allowances for doubtful accounts, stock-based compensation, the estimated useful lives of assets and convertible debt. The management bases the estimates and judgments on historical information and on various other assumptions that management believes are reasonable under the circumstances. Actual results could differ materially from such estimates.

Revenue recognition

Advertising and marketing revenues

Advertising and marketing revenues are derived principally from online advertising, including social display ads and promoted marketing. Social display ad arrangements allow customers to place advertisements on particular areas of the Group’s platform in particular formats and over particular periods of time, which is typically no more than three months. The Group enters into cost per mille (“CPM”), or cost per thousand impressions, advertising arrangements with the customers, under which the Group recognizes revenues based on the number of times that the advertisement has been displayed. The Group also enters into cost per day (“CPD”) advertising arrangements with customers, under which the Group recognizes revenues ratably over the contract periods.

Promoted marketing arrangements are primarily priced based on CPM or cost per engagement (“CPE”). An engagement may include when a user clicks on a link, becomes a follower of the marketing customer account, shares the promoted feed or marks the feed as a favorite. Under the CPM model, customers are obligated to pay when the advertisement is displayed, while under the CPE model, customers are obligated to pay based on the number of engagements with the promoted feed.

Revenues are recognized only when the following criteria have been met: (1) persuasive evidence of an arrangement exists; (2) the price is fixed or determinable; (3) the service is performed; and (4) collectability of the related fee is reasonably assured. The majority of the Group’s revenue transactions are based on standard business terms and conditions, which are recognized net of agency rebates. Advertising arrangements involving multiple deliverables are broken down into single-element arrangements based on their relative selling price for revenue recognition purposes. For multiple-deliverable revenue arrangements, it is required that the arrangement consideration to be allocated to all deliverables at the inception of the arrangement on the following basis: (a) vendor-specific objective evidence (VSOE) of selling price, if it exists, otherwise, (b) third-party evidence (TPE) of the selling price. If neither (a) nor (b) exists, then use (c) management’s best estimate of the selling price of the deliverable. The Group primarily uses VSOE to allocate the arrangement consideration if such selling price is available. For the deliverables that have not been sold separately, the best estimate of the selling price (BESP) is used, which has taken into consideration of the pricing of advertising areas of the Group’s platform with similar popularity and advertisements with similar format and quoted prices from competitors and other market conditions. Revenues recognized with reference to BESP were immaterial for all periods presented. The Group recognizes revenues on the elements delivered and defers the recognition of revenues for the undelivered elements until the remaining obligations have been satisfied.

Revenues from barter transactions are recognized during the period in which the advertisements are displayed on the Group’s properties. Barter transactions in which physical goods or services (other than advertising services) are received in exchange for advertising services are recorded based on the fair values of the goods or services received. Revenues from barter transactions were immaterial for all periods presented.

Value-added services revenues

The Group generates value-added services revenues principally from fee-based services, including game-related services, VIP membership and data licensing. Revenues from these services are recognized over the periods in which the services are performed, provided that no significant obligations remain, collection of the receivable is reasonably assured and the amounts can be accurately estimated.

Game-related services. Game-related service revenues are mostly generated from the sale of virtual items from games operated by the Group. The Group collects payments from the game players in connection with the sale of virtual currency, which are converted into in-game credits (game tokens) that can be used to purchase virtual items in online games. The Group remits certain predetermined percentages of the proceeds to the game developers when the virtual currency is converted into in-game credits.

The Group determines whether the game developers are the primary obligors for the game-related service, based on whether the game developers are responsible for developing, maintaining and updating the game related services and have reasonable latitude to establish the prices of virtual items for which in-game credits are used. Revenue is recorded on a gross basis for games that the Group is acting as the principal in fulfilling all obligations related to the games and revenue is recorded net of predetermined revenue sharing with the game developers for games in which the Group’s primary responsibility is to promote the games of the developers, provide virtual currency exchange service, maintain the platform for game players to easily access the games and offer customer support to resolve registration, log-in, currency exchange and other related issues.

Virtual currencies in general are not refundable once they have been sold unless there are unused in-game credits at the time a game is discontinued. Sale of virtual currencies are recognized as revenues over the estimated consumption period of in-game virtual items, which is typically from a few days to one month after the purchase of in-game credits.

VIP membership. VIP membership is a service package consisting of user certification and preferential benefits, such as daily priority listings and higher quota for following user accounts. Prepaid VIP membership fees are recorded as deferred revenue and recognized as revenue ratably over the contract period of the membership service.

Data licensing. The Group offers data licensing arrangements that allow its customers to access, search and analyze historical and real-time data on its platform. The data licensing arrangement is for a fixed period, typically one year, and such revenue is recognized ratably over the contract period.

Cost of revenues

Cost of revenues consists mainly of costs associated with the maintenance of platform, which primarily include bandwidth and other infrastructure costs, labor cost and turnover taxes levied on the revenues, part of which were allocated from SINA (see Note 1 Reorganization ). The Group presents taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction on a gross basis in the financial statements. The Group is subject to 6.7% Value-Added Tax (“VAT”) and surcharges for its revenues and an additional 3% cultural business construction fees for its advertising and marketing revenues. The total amount of such taxes on its advertising and marketing revenues for the years ended December 31, 2015, 2016 and 2017 were $35.3 million, $49.9 million and $90.6 million, respectively.

Sales and Marketing Expenses

Sales and marketing expenses consist mainly of online and offline advertising and promotional expenses, salary, benefits and commission expenses, and facility expenses. Advertising and promotional expenses generally represent the expenses of promotions of corporate image and product marketing. The Group expenses all advertising and promotional expenses as incurred and classifies these expenses under sales and marketing expenses. For the years ended December 31, 2015, 2016 and 2017, the advertising and promotional expenses were $81.2 million, $92.2 million and $200.6 million, respectively.

Product development expenses

Product development expenses consist mainly of payroll-related expenses and infrastructure costs incurred for enhancement to and maintenance of the Group’s platform, as well as costs associated with new product development and product enhancements, part of which were allocated from SINA (see Note 1 Reorganization ). The Group expenses all costs incurred for the planning and post implementation phases of development and costs associated with repair or maintenance of the existing site or the development of platform content. Since inception, the amount of costs qualifying for capitalization has been immaterial and, as a result, all product development costs have been expensed as incurred.

Stock-based compensation

All stock-based awards to employees and directors, such as stock options and restricted share units (“RSUs”), are measured at the grant date based on the fair value of the awards. Stock-based compensation, net of forfeitures, is recognized as expenses on a straight-line basis over the requisite service period, which is the vesting period.

The Group uses the Black-Scholes option pricing model to estimate the fair value of stock options. The determination of estimated fair value of stock-based payment awards on the grant date using an option pricing model is affected by the fair value of the Company’s ordinary shares as well as assumptions regarding a number of complex and subjective variables. These variables include the expected value volatility of the Company over the expected term of the awards, actual and projected employee stock option exercise behaviors, a risk-free interest rate and expected dividends, if any. Options granted generally vest over four years.

The Group recognizes the estimated compensation cost of restricted share units based on the fair value of its ordinary shares on the date of the grant. The Group recognizes the compensation cost, net of estimated forfeitures, over a vesting term of generally four years for service-based restricted share units. The Group also recognizes the compensation cost of performance-based restricted share units, net of estimated forfeitures, if it is probable that the performance condition will be achieved at the end of each reporting period.

Forfeitures are estimated at the time of grant and revised in subsequent periods if actual forfeitures differ from those estimates. The Group uses historical data to estimate pre-vesting option and records stock-based compensation expense only for those awards that are expected to vest. See Note 6 Stock-based Compensation for further discussion on stock-based compensation.

Taxation

Income taxes

Income taxes are accounted for using the asset and liability approach. Under this approach, income tax expense is recognized for the amount of taxes payable or refundable for the current year. In addition, deferred tax assets and liabilities are recognized for expected future tax consequences of temporary differences between the financial reporting and tax bases of assets and liabilities, and for operating losses and tax credit carry forwards. The Group records a valuation allowance to reduce deferred tax assets to an amount for which realization is more likely than not.

Uncertain tax positions. To assess uncertain tax positions, the Group applies a more likely than not threshold and a two-step approach for the tax position measurement and financial statement recognition. Under the two-step approach, the first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement.

Operating leases

The Group leases office space under operating lease agreements with initial lease terms ranging from six months to five and a half years. Rental expense is recognized from the date of initial possession of the leased property on a straight-line basis over the term of the lease, part of which was allocated from SINA (see Note 1 Reorganization). Certain lease agreements contain rent holidays, which are recognized on a straight-line basis over the lease term. Lease renewal periods are considered on a lease-by-lease basis and are generally not included in the initial lease terms. The allocated rental expenses from SINA for the years ended December 31, 2015, 2016 and 2017, were $3.5 million, $3.9 million and $4.5 million, respectively.

Cash equivalents

The Group considers all highly liquid investments with original maturities of three months or less as cash equivalents. Cash equivalents are comprised of investments in time deposits that mature within three months stated at cost plus accrued interest.

Accounts receivable and allowances for doubtful accounts

Accounts receivable are recorded and carried at the original invoiced amount less an allowance for any potential uncollectible amounts. The Group maintains an allowance for doubtful accounts which reflects its best estimate of amounts that will not be collected. The Group determines the allowance for doubtful accounts based on a historical, rolling average, bad debt rate in the prior period and other factors, such as credit-worthiness of the customers and the age of the receivable balances. The Group also provides specific provisions for bad debts when facts and circumstances indicate that the receivable is unlikely to be collected. If the financial condition of the Group’s customers were to deteriorate, resulting in an impairment of their ability to make payments, more bad debt allowances may be required.

Fair value measurements

Financial instruments

All financial assets and liabilities are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis. Accounting guidance defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities required or permitted to be recorded at fair value, the Group considers the principal or most advantageous market in which it would transact and it considers assumptions that market participants would use when pricing the asset or liability.

Accounting guidance establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Accounting guidance establishes three levels of inputs that may be used to measure fair value:

Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities.

Level 2 applies to assets or liabilities for which there are inputs other than quoted prices included within Level 1 that are observable for the asset or liability such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical asset or liabilities in markets with insufficient volume or infrequent transactions (less active markets); or model-derived valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data.

Level 3 applies to asset or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.

The carrying amount of cash and cash equivalents, short-term investments, accounts receivable due from third parties, accounts receivable due from Alibaba, accounts receivable due from other related parties, amount due from/to SINA, accounts payable, accrued and other liabilities approximates fair value because of their short-term nature. See Note 14 Financial Instruments for additional information.

Long-term investments

Long-term investments are comprised of investments in publicly traded and privately held companies. For long-term investments over which the Group does not have significant influence, the cost method of accounting is used. For long-term investments in shares that are not common stock or in-substance common stock and that do not have readily determinable fair value, the cost method accounting is used. The Group uses the equity method to account for ordinary-share-equivalent equity investments over which it has significant influence but does not own a majority equity interest or otherwise control.

The Group monitors its investments accounted for under the cost method and equity method for other-than-temporary impairment by considering factors such as current economic and market conditions and the operating performance of the business, including current earnings trends, undiscounted cash flows, and other company-specific information, such as recent financing rounds. Determination of the fair value, particularly for investments in privately-held companies whose revenue model is unclear, requires significant judgment to determine appropriate estimates and assumptions. Changes in these estimates and assumptions could affect the calculation of the fair value of the investments and the determination of whether any identified impairment is other-than-temporary. If any impairment is considered other-than-temporary, the Group will write down the asset to its fair value and take the corresponding charge to the consolidated statements of comprehensive income. The Group recorded an impairment charge of $6.6 million, $31.6 million and $4.7 million to the carrying value of long-term investments accounted for under the cost method and equity method for the years ended December 31, 2015, 2016 and 2017, respectively.

The Group invests in marketable equity securities to meet business objectives and intends to hold the securities for more than a year from the balance sheet date. These marketable securities are reported at fair value, classified and accounted for as available-for-sale (“AFS”) securities under long-term investments. The treatment of a decline in the fair value of an individual security is based on whether the decline is other-than-temporary. The Group assesses its available-for-sale securities for other-than-temporary impairment by considering factors including, but not limited to, its ability and intent to hold the individual security, severity of the impairment, expected duration of the impairment and forecasted recovery of fair value. Investments classified as available-for-sale securities are reported at fair value with unrealized gains or losses, if any, recorded in accumulated other comprehensive income (loss) in shareholders’ equity. If the Group determines a decline in fair value is other-than-temporary, the cost basis of the individual security is written down to fair value as a new cost basis and the amount of unrealized loss recorded in accumulated other comprehensive income (loss) will be reclassified to net income in the consolidated statements of comprehensive income. The fair value of the investment would then become the new cost basis of the investment and is not adjusted for subsequent recoveries in fair value. The Group recorded an impairment charge of nil, $4.8 million and nil to AFS securities for the years ended December 31, 2015, 2016 and 2017, respectively.

Business combination

Business combinations are recorded using the purchase method of accounting, and the cost of an acquisition is measured as the aggregate of the fair values at the date of exchange of the assets given, liabilities incurred, and equity instruments issued as well as the contingent considerations and all contractual contingencies as of the acquisition date. The costs directly attributable to the acquisition are expensed as incurred. Identifiable assets, liabilities and contingent liabilities acquired or assumed are measured separately at their fair value as of the acquisition date, irrespective of the extent of any non-controlling interests. The excess of the (i) the total of consideration paid, fair value of the non-controlling interests and acquisition date fair value of any previously held equity interest in the subsidiary acquired over (ii) the fair value of the identifiable net assets of the subsidiary acquired is recorded as goodwill. If the consideration of acquisition is less than the fair value of the net assets of the subsidiary acquired, the difference is recognized directly in the consolidated statements of comprehensive income.

Long-lived assets

Property and equipment

Property and equipment are stated at cost less accumulated depreciation, amortization and impairment, if any. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally from three to four years for computers and equipment and five years for furniture and fixtures. Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the remaining lease term. Depreciation expenses were $19.5 million, $13.3 million and $14.7 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of the identifiable assets and liabilities acquired as a result of the Group’s acquisitions of interests in its subsidiaries and consolidated VIE. The Group assesses goodwill for impairment in accordance with ASC Subtopic 350-20 (“ASC 350-20”), Intangibles - Goodwill and Other: Goodwill, which requires that goodwill be tested for impairment at the reporting unit level at least annually and more frequently upon the occurrence of certain events, as defined by ASC 350-20. US GAAP provides the option to apply the qualitative assessment first and then the quantitative assessment, if necessary, or to apply the quantitative assessment directly. The qualitative approach starts the goodwill impairment test by assessing qualitative factors, which by taking into consideration of macroeconomics, overall financial performance, industry and market conditions and the share price of the Group, to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If so, the quantitative impairment test is performed; otherwise, no further testing is required. When the Group performs the quantitative impairment test, the Group firstly determines whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. For those reporting units where it is determined that it is more likely than not that their fair values are less than the units’ carrying amounts, the Group performs the second step of a two-step quantitative goodwill impairment test to allocate the fair value of reporting units to all of the assets and liabilities of that unit (including any unrecognized intangible assets) as if the reporting unit had been acquired in a business combination. Application of a goodwill impairment test requires significant management judgment, including the identification of reporting units, assigning assets and liabilities to reporting units, assigning goodwill to reporting units, and determining the fair value of each reporting unit. Judgment in estimating the fair value of reporting units includes estimating future cash flows, determining appropriate discount rates and making other assumptions. Changes in these estimates and assumptions could materially affect the determination of fair value for each reporting unit.

Intangible assets other than goodwill

Intangible assets arising from acquisitions are recognized at fair value upon acquisition and amortized on a straight-line basis over their estimated useful lives, generally from two to five years. Long-lived assets and certain identifiable intangible assets other than goodwill to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. Measurement of any impairment loss for long-lived assets and certain identifiable intangible assets that management expects to hold or use is based on the amount by which the carrying value exceeds the fair value of the asset. Judgment is used in estimating future cash flows, determining appropriate discount rates and making other assumptions. Changes in these estimates and assumptions could materially affect the determination of the asset’s fair value.

Convertible debt

The Group determines the appropriate accounting treatment of its convertible debt in accordance with the terms in relation to the conversion feature. After considering the impact of such features, the Group may account for such instrument as a liability in its entirety, or separate the instrument into debt and equity components following the respective guidance described under ASC 815 Derivatives and Hedging and ASC 470 Debt.

The debt discount, if any, together with related issuance cost are subsequently amortized as interest expense over the contractual life. The Group presented the issuance costs of debt as a direct deduction from the related debt during the periods presented.

Deferred revenues

Deferred revenues consist of contractual billings in excess of recognized revenue and payments received in advance of revenue recognition, which are mainly from the customer advance of the advertising and marketing services and the sales of the fee-based services, such as virtual currency or in-game virtual items sold for game related services and VIP membership.

Non-controlling interests

For the Company’s majority-owned subsidiaries and VIE, non-controlling interests are recognized to reflect the portion of their equity that is not attributable, directly or indirectly, to the Company as the controlling shareholder. To reflect the economic interest held by non-controlling shareholders, net loss attributable to the non-controlling ordinary shareholders is recorded as non-controlling interests in the Company’s consolidated statements of comprehensive income. Non-controlling interests are classified as a separate line item in the equity section of the Company’s consolidated balance sheets and have been separately disclosed in the Company’s consolidated financial statements to distinguish the interests from that of the Company.

Foreign currency

The Company’s reporting currency and functional currency are the U.S. dollar. The Group’s operations in China and in international regions use their respective currencies as their functional currencies. The financial statements of these subsidiaries are translated into U.S. dollars using period-end rates of exchange for assets and liabilities and average rates of exchange in the period for revenues, costs and expenses. Translation gains and losses are recorded in accumulated other comprehensive income (loss) as a component of shareholders’ equity. Translation gains or losses are not released to net income unless the associated net investment has been sold, liquidated, or substantially liquidated.

Foreign currency transactions denominated in currencies other than the functional currency are translated into the functional currency using the exchange rate prevailing on the transactions dates. Monetary assets and liabilities denominated in foreign currencies are translated into the functional currency using the applicable exchange rates at the balance sheet dates. Net gains and losses resulting from foreign exchange transactions are included in interest and other income, net.

Foreign currency translation adjustments included in the Group’s consolidated statements of comprehensive income for the years ended December 31, 2015 and 2016 were loss of $7.9 million and $18.9 million, respectively, and $37.8 million gain for the year ended December 31, 2017. Net foreign currency transaction gains or losses arise from transacting in a currency other than the functional currency of the entity and the amounts recorded were immaterial for each of the periods presented.

Net Income per share

Basic net income per share is computed using the weighted average number of ordinary shares outstanding during the period. Options and RSUs are not considered outstanding in computation of basic earnings per share. Diluted net income per share is computed using the weighted average number of ordinary shares and potential ordinary shares outstanding during the period, which include options to purchase ordinary shares, restricted share units and conversion of the convertible debt. The computation of diluted net income per share does not assume conversion, exercise, or contingent issuance of securities that would have an anti-dilutive effect (i.e. an increase in earnings per share amounts or a decrease in loss per share amounts) on net income per share. The Group uses the two-class method to calculate net income per share though both classes share the same rights in dividends. Therefore, basic and diluted earnings per share are the same for both classes of ordinary shares.

Segment reporting

In accordance with ASC 280, Segment Reporting, the Group’s chief operating decision maker (“CODM”), the Chief Executive Officer, reviews the consolidated results when making decisions about allocating resources and assessing performance of the Group as a whole. The Group currently operates and manages its business in two principal business segments globally—advertising and marketing services and value-added services. Information regarding the business segments provided to the Group’s CODM is at the revenue level and the Group currently does not allocate operating costs or assets to its segments, as its CODM does not use such information to allocate resources or evaluate the performance of the operating segments. As the Group’s long-lived assets are substantially all located in the PRC and substantially the Group’s revenues are derived from within the PRC, no geographical information is presented.

Concentration of risks

Concentration of credit risk. Financial instruments that potentially subject the Group to a concentration of credit risk consist primarily of cash and cash equivalents, short-term investments and accounts receivable. In addition, with the majority of its operations in China, the Group is subject to RMB currency risk and offshore remittance risk, both of which have been difficult to hedge and the Group has not done so. The Group limits its exposure to credit loss by depositing its cash and cash equivalents with financial institutions in the US, PRC and Hong Kong, which are among the largest and most respected with high ratings from internationally-recognized rating agencies, that management believes are of high credit quality. The Group periodically reviews these institutions’ reputations, track records and reported reserves.

As of December 31, 2016 and 2017, the Group had $393.6 million and $1.79 billion, respectively, in cash and bank time deposits (with terms generally up to twelve months) with large domestic banks in China. China promulgated a Bankruptcy Law that came into effect on June 1, 2007, which contains a separate article expressly stating that the State Council may promulgate implementation measures for the bankruptcy of Chinese banks based on the Bankruptcy Law. Under the Bankruptcy Law, a Chinese bank may go bankrupt. In addition, since China’s concession to WTO, foreign banks have been gradually permitted to operate in China and have become significant competitors to Chinese banks in many aspects, especially since the opening of RMB business to foreign banks in late 2006. Therefore, the risk of bankruptcy on Chinese banks in which the Group holds cash and bank deposits has increased. In the event that a Chinese bank that holds the Group’s deposits goes bankrupt, the Group is unlikely to claim its deposits back in full, since it is unlikely to be classified as a secured creditor to the bank under the PRC laws.

Alibaba accounted for 30%, 9% and 7% of the Group’s revenues for the years ended December 31, 2015, 2016 and 2017, respectively. No other customer nor advertising agency accounted for 10% or more of the Group’s revenues. The Group’s top 10 advertising agencies contributed to 15%, 22%, and 23% of the Group’s revenues for the years ended December 31, 2015, 2016, and 2017, respectively.

As of December 31, 2016 and 2017, substantially all accounts receivable were derived from the Group’s China operations. Excluding accounts receivable due from Alibaba and other related parties, accounts receivable primarily consists of amounts due from advertising agencies and direct customers. Alibaba accounted for 21% and 25%, respectively, of the Group’s net accounts receivables as of December 31, 2016 and 2017, while one customer accounted for 15% and 10%, respectively, at the same dates.

Concentration of foreign currency risks. The majority of the Group’s operations were in RMB. As of December 31, 2016 and 2017, the Group’s cash, cash equivalents and short-term investments balance denominated in RMB was $335.7 million and $871.2 million, accounting for 85% and 49% of the Group’s total cash, cash equivalents and short-term investments balance. As of December 31, 2016 and 2017, the Group’s aggregate net accounts receivable balance (including accounts receivable due from third parties, Alibaba and other related parties) denominated in RMB was $115.3 million and $170.1 million, respectively, accounting for almost all of its net accounts receivable balance. As of December 31, 2016 and 2017, the Group’s current liabilities balance denominated in RMB was $267.8 million and $475.6 million, accounting for 96% and 98% of its total current liabilities balance. Accordingly, the Group may experience economic losses and negative impacts on earnings and equity as a result of exchange rate fluctuations of the RMB. Moreover, the Chinese government imposes controls on the convertibility of the RMB into foreign currencies and, in certain cases, the remittance of currency out of the PRC. The Group may experience difficulties in completing the administrative procedures necessary to remit its RMB out of the PRC and convert it into foreign currency.

Recent accounting pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued, ASU 2014-09, “Revenue from Contracts with Customers (Topic 606).” The guidance substantially converges final standards on revenue recognition between the FASB and the International Accounting Standards Board providing a framework on addressing revenue recognition issues and, upon its effective date, replaces almost all exiting revenue recognition guidance, including industry-specific guidance, in current U.S. generally accepted accounting principles. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The Group currently anticipates adopting the standard using the modified retrospective method, which means that revenues for 2016 and 2017 will be reported on a historical basis and revenues for 2018 will be reported on the new basis. The Group has substantially completed the assessments related to the standard. The main impact will be the presentation of value added tax recognized in revenue from “gross” to “net”, resulting in equal decrease in revenues and cost of revenues, and recognition of revenues and expenses at fair value for advertising barter transactions, resulting in the increase of revenue and advertising expenses. In aggregate, the Group does not expect the new revenue standard will have a material impact on net income level and it expects the cumulative-effect adjustment on the retained earnings as of January 1, 2018 related to the initial application of the new revenue standard to be immaterial.

In January 2016, the FASB issued updated guidance on financial instruments, ASU No. 2016-01, which intends to improve the recognition and measurement of financial instruments. Most prominent among the changes in the standard is the requirement for changes in the fair value of investments, with certain exceptions, to be recognized through net income rather than other comprehensive income. The Group plans to adopt the new guidance beginning in the first quarter of fiscal year 2018. Adoption of the standard will be applied through a cumulative-effect adjustment to retained earnings as of the effective date. After adoption of the new standard, the Group will measure long-term investments other than equity method ones at fair value from quarter to quarter and will record the fair value change in net income for the period. For those investments without readily determinable fair values, the Group will elect to record these investments at cost, less impairment, and plus or minus subsequent adjustments for observable price changes. Changes in the basis of these investments will be reported in current earnings. The cumulative-effect adjustment on the retained earnings as of January 1, 2018 is expected to be immaterial and the Group anticipates the quarterly fair value change may vary significantly afterwards.

In February 2016, the FASB issued a new standard on leases, ASU No. 2016-02, which requires that a lessee recognize the assets and liabilities that arise from operating leases. A lessee should recognize a liability to make lease payments (the lease liability) and a right-of use representing its right to use the underlying asset for the lease term in the statements of financial position. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. In transition, lessees are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. This standard will be effective for the Group beginning the first quarter of fiscal year 2019. The Group is currently evaluating the impact that this new standard will have on its consolidated financial statements.

In August 2016, the FASB issued ASU No. 2016-15, which clarifies and includes specific guidance to address diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The amendments will be effective beginning the first quarter of fiscal year 2018. Early adoption of the amendments is permitted. The amendments in this ASU should be applied using a retrospective transition method to each period presented. The Group will adopt the amendments in the fiscal year of 2018 and does not expect a significant impact on its consolidated financial statements from the amendments.

In January 2017, the FASB issued ASU No. 2017-01, which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The amendments should be applied prospectively on or after the effective date. No disclosures are required at transition. The Group plans to adopt the new standard beginning in the first quarter of fiscal year 2018 and does not expect a significant impact the amendments will have on its consolidated financial statements.

In January 2017, the FASB issued ASU No. 2017-04, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the amendments, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying value, which eliminates the current requirement to calculate a goodwill impairment charge by comparing the implied fair value of goodwill with its carrying amount. The amendments will be effective beginning the first quarter of fiscal year 2020. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The amendments should be applied on a prospective basis. The Group is currently evaluating the impact the new amendments will have on its consolidated financial statements.

In May 2017, the FASB issued ASU No. 2017-09, which clarifies the scope of modification accounting for share-based compensation (Topic 718). The new standard indicates that an entity should account for the effects of a modification under certain conditions. The Group plans to adopt the new standard beginning in the first quarter of fiscal year 2018 and does not expect a significant impact this new standard will have on its consolidated financial statements.

Cash, Cash Equivalents and Short-term Investments

12 Months Ended

Dec. 31, 2017

Cash, Cash Equivalents and Short-term Investments

Cash, Cash Equivalents and Short-term Investments

3. Cash, Cash Equivalents and Short-term Investments

Cash, cash equivalents and short-term investments consist of the following:

	As of December 31,
	2016		2017
	(In thousands)
Cash and cash equivalents:
Cash	$	364,766	$	1,000,953


Short-term investments:
Bank time deposits	31,188		791,730


Total cash, cash equivalents and short-term investments	$	395,954	$	1,792,683

The carrying amounts of cash, cash equivalents and short-term investments approximate fair value. Interest income was $5.5 million, $7.6 million and $17.9 million for the years ended December 31, 2015, 2016 and 2017, respectively. The maturity dates for the time deposits were within one year.

Long-term Investments

12 Months Ended

Dec. 31, 2017

Long-term Investments

Long-term Investments

4. Long-term Investments

Long-term investments comprised of investments in privately held and publicly traded companies. The following sets forth the changes in the Group’s long-term investments:

	Cost Method			Equity Method			Available-for-Sale Securities			Total
	(In thousands)

Balance at December 31, 2014	$	50,594		$	154		$	13,029		$	63,777
Investments made	252,256			—			—			252,256
Loss from equity method investment	—			(6		)	—			(6		)
Disposal of investments	(13,134		)	—			—			(13,134		)
Impairment on investments	(6,608		)	—			—			(6,608		)
Unrealized loss	—			—			(198		)	(198		)
Currency translation adjustment	(1,401		)	(7		)	—			(1,408		)


Balance at December 31, 2015	$	281,707		$	141		$	12,831		$	294,679
Investments made	147,767			4,324			—			152,091
Loss from equity method investment	—			(130		)	—			(130		)
Disposal of investments	(6,010		)	—			(5,000		)	(11,010		)
Impairment on investments	(31,586		)	—			—			(31,586		)
Unrealized loss	—			—			(2,557		)	(2,557		)
Currency translation adjustment	(1,548		)	(6		)	—			(1,554		)


Balance at December 31, 2016	$	390,330		$	4,329		$	5,274		$	399,933
Investments made	31,776			22,307			—			54,083
Gain from equity method investment	—			1,030			—			1,030
Dividend received from equity method investment	—			(267		)	—			(267		)
Impairment on investments	(4,747		)	—			—			(4,747		)
Unrealized loss	—			—			(995		)	(995		)
Currency translation adjustment	2,997			303			—			3,300


Balance at December 31, 2017	$	420,356		$	27,702		$	4,279		$	452,337

As of December 31, 2016 and 2017, investments accounted for under the cost method were $390.3 and $420.4 million, respectively. Investments were accounted for under the cost method if the Group had no significant influence or if the underlying shares were not considered in substance ordinary shares and had no readily determinable fair value.

For the year ended December 31, 2017, the Group made investments in private high tech companies totaling $54.1 million, which were accounted for under the cost method or equity method. These investments were made, in general to expand and strengthen the Group’s ecosystem.

Investments in marketable securities are held as available-for-sale and reported at fair value due to changes in quoted market price. The Group made a $15.1 million investment in 2014 and accounted for it as an AFS investment. In 2016, the Group disposed part of the investment and recognized an impairment charge of $4.8 million to net income, based on the severity and duration of the decline from the carrying value. As of December 31, 2016 and 2017, the fair value of the AFS investment was $5.3 million and $4.3 million, respectively.

The Group performs an impairment assessment on its investments and determines whether investment impairment, if any, is other-than-temporary based on changes in quoted market price or other impairment indicators. The Group recorded impairment charges of $8.0 million, $40.2 million, and $4.7 million on the carrying value of its long-term investments and prepayment for the years ended December 31, 2015, 2016 and 2017, respectively, as a result of the investments not performing to expectation or them becoming incapable of making repayment. The investment impairment in 2016 included a $19.0 million write-off on an online-to-offline business and a $10.5 million write-off on an employment-oriented social company.

Acquisitions

12 Months Ended

Dec. 31, 2017

Acquisitions

Acquisitions

5. Acquisitions

On June 30, 2015, the Group acquired a 55% and 85% equity interest in two investment funds (“Weibo funds”) for a total cash consideration of $22.0 million from SINA. The Weibo funds engage in investing in high-tech startups related to the Weibo business. The Group engaged an independent valuation firm to assist management in its valuation of the purchase price allocation. Since Weibo and the Weibo Funds were controlled by SINA before and after the acquisition, the transaction was accounted for as a business combination between entities under common control. In accordance with ASC Subtopic 805-50, the Group’s consolidated financial statements included the acquired assets and liabilities of the Weibo Funds at their historical carrying amounts and were prepared as if the current corporate structure had been in place throughout the periods presented. The Group had one immaterial acquisition in 2017. No new acquisition incurred in 2016.

The following sets forth the changes in the Group’s goodwill by segment:

	Advertising & Marketing		Other			Total
	(In thousands)
Balance as of December 31, 2015	$	—	$	11,117		$	11,117
Currency translation adjustment	—		(851		)	(851		)

Balance as of December 31, 2016	$	—	$	10,266		$	10,266

New acquisition	—		2,318			2,318
Currency translation adjustment	—		836			836

Balance as of December 31, 2017	$	—	$	13,420		$	13,420

As of December 31, 2017, the Group performed a qualitative analysis on the goodwill arising from the acquisition taking into consideration the events and circumstances listed in ASC350 Intangibles—Goodwill and Other, including consideration of macroeconomic factors, industry and market conditions, share price of the Group, and overall financial performance, in addition to other entity-specific factors. Based on the analysis, the Group determined that it was not necessary to perform a quantitative goodwill impairment assessment and concluded that no impairment indicators on its goodwill were noted during the period presented.

As of December 31, 2017, the Group’s intangible assets totaled $0.5 million, mainly consisted of acquired game-related platform technology and a non-compete agreement. The amortization expense for the years ended December 31, 2015, 2016 and 2017 was $1.5 million, $0.7 million and $0.6 million, respectively. As of December 31, 2017, estimated amortization expenses for future periods are expected as follows:

Year Ended December 31,	(In thousands)
2018	$	517
2019 and thereafter	—

Total expected amortization expense	$	517

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Stock-Based Compensation

Stock-Based Compensation

6. Stock-Based Compensation

In August 2010, the Company adopted the 2010 Share Incentive Plan (the “2010 Plan”), which has a term of ten years and permits the grant of options, share appreciation rights, restricted shares and restricted share units of the Company to employees, directors and consultants of the Company and its affiliates. Under the plan, a total of 35 million ordinary shares were initially reserved for issuance. The maximum number of ordinary shares available for issuance will be reduced by one share for every one share issued pursuant to a share option or share appreciation right and by 1.75 share for every one share issued as restricted shares or pursuant to a restricted shares unit. In March 2014, the 2010 Plan was terminated and all remaining shares were forwarded to the 2014 Plan.

In March 2014, the Company adopted the 2014 Share Incentive Plan (the “2014 Plan”), which was funded by the remaining 4.6 million shares from the 2010 Plan plus an additional 1.0 million shares. On January 1, 2015, shares in the 2014 Plan, which have a term life of ten years, were allowed a one-time increase in the amount equal to 10% of the total number of Weibo shares issued and outstanding on a fully-diluted basis as of December 31, 2014. Each share in the 2014 Plan pool allows for a grant of a restricted share unit or option share. The Company intends to use such share incentive plan to attract and retain employee talent.

The following table sets forth the stock-based compensation included in each of the relevant accounts:

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Cost of revenues	$	1,196	$	2,616	$	3,716
Sales and marketing	3,209		5,357		8,264
Product development	10,210		15,076		21,879
General and administrative	11,784		13,853		14,178

	$	26,399	$	36,902	$	48,037

Stock based compensation related to the grants were amortized generally over four years on a straight-line basis with $26.4 million, $36.9 million and $48.0 million expensed for the years ended December 31, 2015, 2016 and 2017, respectively.

The following table sets forth a summary of the number of shares available for issuance:

	Shares Available
	(In thousands)
December 31, 2014	2,738
Addition	21,684
Granted*	(4,851	)
Cancelled/expired/forfeited	646


December 31, 2015	20,217
Addition	—
Granted*	(1,917	)
Cancelled/expired/forfeited	578


December 31, 2016	18,878
Addition	—
Granted*	(736	)
Cancelled/expired/forfeited	398


December 31, 2017	18,540

In 2015, 4.9 million restricted share units and no options were granted under the 2014 Plan. In 2016, 1.9 million restricted share units and no options were granted under the 2014 Plan. In 2017, 0.7 million restricted share units and no options were granted under the 2014 Plan.

Stock Options

The following table sets forth a summary of option activities under the Company’s stock option program:

	Options Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
	(In thousands)				(In years)	(In thousands)
December 31, 2014	14,330		$	1.28	3.2	$	185,684
Granted	—		$	—
Exercised	(7,309	)	$	1.11
Cancelled/expired/forfeited	(718	)	$	3.22


December 31, 2015	6,303		$	1.26	2.4	$	114,975
Granted	—		$	—
Exercised	(3,625	)	$	1.10
Cancelled/expired/forfeited	(91	)	$	3.37


December 31, 2016	2,587		$	1.41	1.6	$	101,403
Granted	—		$	—
Exercised	(2,122	)	$	1.04
Cancelled/expired/forfeited	(28	)	$	0.68


December 31, 2017	437		$	3.24	2.0	$	43,800


Vested and expected to vest as of December 31, 2016	2,572		$	1.40	1.6	$	100,819
Exercisable as of December 31, 2016	2,433		$	1.28	1.4	$	95,678

Vested and expected to vest as of December 31, 2017	437		$	3.24	2.0	$	43,800
Exercisable as of December 31, 2017	437		$	3.24	2.0	$	43,800

The total intrinsic value of options exercised for the years ended December 31, 2015, 2016 and 2017 was $106.2 million, $129.3 million and $135.2 million, respectively. The intrinsic value is calculated as the difference between the market value on the date of exercise and the exercise price of the shares. As reported by the NASDAQ Global Selected Market, the Company’s ending stock price as of December 31, 2015, 2016 and 2017 was $19.50, $40.60 and $103.46, respectively. Cash received from the exercise of stock option during the years ended December 31, 2015, 2016 and 2017 was $7.8 million, $4.2 million and $2.3 million, respectively.

As of December 31, 2016 and 2017, unrecognized compensation cost, adjusted for estimated forfeitures, related to non-vested stock options granted to the Group’s employees and directors was $1.1 million and nil, respectively. All compensation cost related to stock options has been fully amortized in 2017.

Information regarding stock options outstanding is summarized below:

Range of Exercise Prices	Options Outstanding	Weighted Average Exercise Price		Options Exercisable	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
	(In thousands)			(In thousands)			(In years)
As of December 31, 2016
$ 0.36 - $0.41	1,639	$	0.36	1,639	$	0.36	0.7
$ 0.96 - $1.80	79	$	0.97	79	$	0.97	1.2
$ 3.25 - $3.36	341	$	3.33	338	$	3.33	2.5
$ 3.43 - $3.50	528	$	3.48	377	$	3.48	3.7

	2,587	$	1.41	2,433	$	1.28	1.6


As of December 31, 2017
$ 0.96 - $1.80	31	$	0.97	31	$	0.97	0.2
$ 3.25 - $3.36	179	$	3.33	179	$	3.33	1.4
$ 3.43 - $3.50	227	$	3.48	227	$	3.48	2.6

	437	$	3.24	437	$	3.24	2.0

Restricted Share Units

Summary of Performance-Based Restricted Share Units

The following table sets forth a summary of performance-based restricted share unit activities:

	Shares Granted		Weighted-Average Grant Date Fair Value
	(In thousands)
December 31, 2015	—		$	—
Awarded	111		$	27.00
Cancelled	(3	)	$	27.00


December 31, 2016	108		$	27.00
Awarded	155		$	50.45
Vested	(102	)	$	27.00
Cancelled	(32	)	$	46.42


December 31, 2017	129		$	50.32

As of December 31, 2016 and 2017, unrecognized compensation cost, adjusted for estimated forfeitures, related to performance-based restricted share units granted to the Company’s employees there was $0.3 million and $0.7 million, respectively. No performance-based RSUs were granted in 2015.

Summary of Service-Based Restricted Share Units

The following table sets forth a summary of service-based restricted share unit activities:

	Shares Granted		Weighted- Average Grant Date Fair Value
	(In thousands)
December 31, 2014	3,507		$	16.44
Awarded	4,851		$	12.41
Vested	(1,211	)	$	14.69
Cancelled	(646	)	$	14.18


December 31, 2015	6,501		$	13.98
Awarded	1,806		$	24.94
Vested	(2,274	)	$	14.73
Cancelled	(575	)	$	14.58


December 31, 2016	5,458		$	17.23
Awarded	581		$	62.87
Vested	(2,406	)	$	17.01
Cancelled	(366	)	$	17.72


December 31, 2017	3,267		$	25.45

As of December 31, 2017, unrecognized compensation cost, adjusted for estimated forfeitures and related to non-vested, service-based restricted share units granted to the Company’s employees and directors, was $66.7 million. This cost is expected to be recognized over a weighted-average period of 2.7 years. The total fair value based on the vesting date of the restricted share units vested was $17.8 million, $33.5 million and $40.9 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Other Balance Sheet Components

12 Months Ended

Dec. 31, 2017

Other Balance Sheet Components

Other Balance Sheet Components

7. Other Balance Sheet Components

	As of December 31,
	2015		2016			2017
	(In thousands)
Accounts receivable, net:
Due from third parties			$	66,701		$	105,686
Due from Alibaba			24,293			42,832
Due from other related parties			31,589			29,696


Total gross amount			$	122,583		$	178,214
Allowance for doubtful accounts:
Balance at the beginning of the year	(2,440	)	(1,375		)	(6,529		)
Reversal (additional provision) charged to expenses, net	368		(7,787		)	(5,478		)
Write-off	697		2,633			3,893


Balance at the end of the year	(1,375	)	(6,529		)	(8,114		)

			$	116,054		$	170,100


Prepaid expenses and other current assets:
Rental and other deposits			$	3,965		$	2,233
Prepayment for investments			24,953			20,881
Advertising prepayment			5,267			3,959
Prepayment to outsourced service providers			4,043			5,369
Amounts deposited by users*			21,203			25,277
Content fees			2,111			7,393
Others			5,122			4,121

			$	66,664		$	69,233


Property and equipment, net:
Computers and equipment			$	94,170		$	113,558
Leasehold improvements			2,054			4,321
Furniture and fixtures			922			1,241
Others			1,655			2,574


Property and equipment, gross			98,801			121,694
Less: Accumulated depreciation			(75,985		)	(87,901		)

			$	22,816		$	33,793


Accrued and other liabilities**:
Payroll and welfare			$	33,786		$	57,848
Marketing expenses			40,968			53,380
Payroll withholding taxes			3,547			3,547
Sales rebates			31,598			60,663
Professional fees			4,255			6,170
VAT and other tax payable			35,728			51,563
Payable to other service providers			1,457			362
Amounts due to users*			21,203			25,277
Others			7,600			9,805

			$	180,142		$	268,615

* Weibo wallet enables users to conduct interest-generation activities on Weibo, such as handing out “red envelopes” and coupons to users and purchase different types of products and services on Weibo, including those offered by the Group, such as marketing services and VIP membership, and those offered by Weibo’s platform partners, such as e-commerce merchandises, financial products and virtual gifts. Amounts deposited by users primarily represent the receivables temporarily held in Weibo’s account on a third party online payment platform for Weibo wallet users. Amounts due to users represent the balances that are payable on demand to Weibo wallet users and therefore are reflected as current liability on the consolidated balance sheets.

** Include amounts due to third parties, employees, related parties (see Note 9) and Weibo wallet users.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

Income Taxes

8. Income Taxes

The Company is registered in the Cayman Islands and mainly operates in two taxable jurisdictions—the PRC and Hong Kong.

The Group’s income before income taxes is as follows:

	Year Ended December 31,
	2015			2016			2017
	(In thousands, except percentage)
Income before income tax expenses	$	36,780		$	109,980		$	417,111
Loss from non-China operations	$	(28,016	)	$	(60,193	)	$	(52,261	)
Income from China operations	$	64,796		$	170,173		$	469,372
Income tax expense applicable to China operations	$	2,591		$	4,316		$	66,746
Effective tax rate for China operations	4.0		%	2.5		%	14.2		%

The Company generated the majority of its operating income from PRC operations and has recorded income tax provision for the periods presented. Stock-based compensation was recorded in the Company’s loss from non-China operations. Loss from non-China operations in 2016 included a loss of $23.8 million from investment impairments.

Cayman Islands

Under the current tax laws of the Cayman Islands, the Company is not subject to tax on income or capital gain. In addition, upon payments of dividends by the Company to its shareholders, no Cayman Islands withholding tax is required.

Hong Kong

Weibo HK is subject to taxes in Hong Kong at 16.5% for all the periods presented. As of December 31, 2017, the Company’s Hong Kong subsidiary had a net operating loss of $2.5 million, which can be carried forward indefinitely to offset future taxable income. Also as of December 31, 2017, deferred tax assets of Weibo HK consist mainly of net operating loss carried forward, for which a full valuation allowance was provided. Management believes it is more likely than not that these assets will not be realized in the future.

China

Effective January 1, 2008, the Enterprise Income Tax Law (the “EIT Law”) in China unifies the enterprise income tax rate for the entities incorporated in China at 25%, unless they are eligible for preferential tax treatment. On February 22, 2008, relevant governmental regulatory authorities released the qualification criteria, application procedures and assessment processes for “software enterprise,” which can enjoy an income tax exemption for two years beginning with its first profitable year and a 50% tax reduction, at a rate of 12.5% for the subsequent three years. The Group’s WFOE qualifies as a software enterprise and, thus, enjoyed an income tax exemption in 2015 and 2016, and a reduced enterprise income tax rate of 12.5% in 2017.

The EIT Law also provides that an enterprise established under the laws of a foreign country or region but whose “de facto management body” is located in the PRC be treated as a resident enterprise for PRC tax purposes and consequently be subject to the PRC income tax at the rate of 25% for its global income. The Implementing Rules of the EIT Law merely define the location of the “de facto management body” as “the place where the exercising, in substance, of the overall management and control of the production and business operation, personnel, accounting, properties, etc., of a non-PRC company is located.” Based on a review of surrounding facts and circumstances, the Group does not believe that it is likely that its operations outside of the PRC be considered a resident enterprise for PRC tax purposes. However, due to limited guidance and implementation history of the EIT Law, should Weibo be treated as a resident enterprise for PRC tax purposes, the Company will be subject to PRC tax on worldwide income at a uniform tax rate of 25% retroactive to January 1, 2008.

The EIT Law also imposes a withholding income tax rate of 10% on dividends distributed by a WFOE to its immediate holding company outside of China, if such immediate holding company is considered as a non-resident enterprise without any establishment or place within China or if the received dividends have no connection with the establishment or place of such immediate holding company within China, unless such immediate holding company’s jurisdiction of incorporation has a tax treaty with China that provides for a different withholding arrangement. The Cayman Islands, where the Company incorporated, does not have such tax treaty with China. According to the arrangement between Mainland China and Hong Kong Special Administrative Region on the Avoidance of Double Taxation and Prevention of Fiscal Evasion in August 2006, dividends paid by a WFOE in China to its immediate holding company in Hong Kong will be subject to withholding tax at a rate of no more than 5% (if the foreign investor owns directly at least 25% of the shares of the WFOE). The State Administration of Taxation further promulgated Circular 601 on October 27, 2009, which provides that tax treaty benefits will be denied to “conduit” or shell companies without business substance and that a beneficial ownership analysis will be used based on a “substance-over-form” principle to determine whether or not to grant the tax treaty benefits.

The operations of the Group’s WFOE in China is invested and held by Weibo HK. If the Company is regarded as a non-resident enterprise and Weibo HK is regarded as a resident enterprise, then Weibo HK may be required to pay a 10% withholding tax on any dividends payable to the Company. If Weibo HK is regarded as a non-resident enterprise, then Weibo Technology may be required to pay a 5% withholding tax for any dividends payable to Weibo HK. However, it is still unclear at this stage whether Circular 601 applies to dividends from Weibo Technology paid to Weibo HK. If Weibo HK were not considered as “beneficial owners” of any dividends from Weibo Technology, the dividends payable to Weibo HK would be subject to a withholding tax of 10%. In accordance with accounting guidance, all undistributed earnings are presumed to be transferred to Weibo Corporation and are subject to the withholding taxes. The current policy approved by the Company’s board of directors allows the Group to distribute PRC earnings offshore only if the Group does not have to pay a dividend tax. As of December 31, 2017, the Group did not record any withholding tax for its PRC subsidiaries.

Composition of income tax expenses for China operations

The following table sets forth current and deferred portion of income tax expenses (benefits) of the Company’s China subsidiaries, VIE and VIE’s subsidiaries:

	Years Ended December 31,
	2015			2016			2017
	(In thousands)
Deferred tax benefits	$	(977	)	$	(4,630	)	$	(1,503	)
Current income tax expenses	3,568			8,946			68,249


Income tax expenses	$	2,591		$	4,316		$	66,746

Reconciliation of the statutory tax rate to the effective tax rate for China operations

The following table sets forth reconciliation between the statutory EIT rate and the effective tax rate for China operations:

	Year Ended December 31,
	2015		2016		2017
Statutory EIT rate	25.0	%	25.0	%	25.0	%
Effect on tax holiday and preferential tax treatment	(24.2	) %	(29.6	)%	(11.6	)%
Permanent differences	0.5	%	1.2	%	0.2	%
Change in valuation allowance	2.7	%	5.9	%	0.6	%


Effective tax rate for China operations	4.0	%	2.5	%	14.2	%

The provision for income taxes for the years ended December 31, 2015, 2016 and 2017 differs from the amounts computed by applying the statutory EIT rate primarily due to the tax exemption and preferential tax treatment of the WFOE, Weibo Technology, as a qualified software enterprise for the periods presented. For the years ended December 31, 2015 and 2016, Weibo Technology was tax exempted for $15.7 million and $50.4 million, respectively. For the year ended December 31, 2017, Weibo Technology enjoyed a tax reduction of $52.6 million due to the preferential tax treatment. The tax exemption and reduction in the three-year period ended December 31, 2017 resulted in an effect of $0.08, $0.23 and $0.25 on basic net income per share in 2015, 2016 and 2017, respectively.

Deferred tax assets and liabilities

The following table sets forth the significant components of deferred tax assets and liabilities for China operations:

	As of December 31,
	2016			2017
	(In thousands)
Deferred tax assets:
Net operating loss carry forwards	$	32,158		$	10,280
Less: valuation allowance	(32,158		)	(10,280		)
Depreciation, accounts receivable, accrued and other liabilities	13,957			19,931
Less: valuation allowance	(8,576		)	(11,629		)


Net deferred tax assets (included in other assets)	$	5,381		$	8,302


Deferred tax liabilities:
Acquired intangible assets	$	274		$	129
Depreciation	362			527
Others	181			1,224


Total deferred tax liabilities	$	817		$	1,880

Valuation allowance is provided against deferred tax assets when the Group determines that it is more likely than not that the deferred tax assets will not be utilized in the future. In making such determination, the Group considered factors including (i) future reversals of existing taxable temporary differences; (ii) future taxable income exclusive of reversing temporary differences and carry forwards; and (iii) tax planning strategies. The valuation allowance on deferred tax assets as of December 31, 2016 and 2017 was $40.7 million and $21.9 million, respectively. The change in valuation allowance was primarily due to bad debt expenses and investment impairment charges, as well as the expiration of net operating loss carry forward. Historically, deferred tax assets were valued using the statutory rate of 25%. As of December 31, 2016 and 2017, the Group had net operating loss carry forwards for China operations totaling $129.3 million and $41.1 million, respectively, for which full valuation allowance was provided. The net operating loss carry forwards as of December 31, 2017 consisted of net operating loss carry forwards in the amount of $18.6 million resulting from the Company’s carve-out from SINA and cumulative loss of the Company’s entities in the amount of $22.5 million. In 2017, $96.2 million of the net operating loss carry forwards expired and none was utilized. Net operating loss carry forwards for China operations as of December 31, 2017 will expire, if unused, in the years ending December 31, 2018 through December 31, 2022. The net operating loss of the carve-out from SINA will expire, if unused, in the year ending December 31, 2018.

Related Party Transactions

12 Months Ended

Dec. 31, 2017

Related Party Transactions

Related Party Transactions

9. Related Party Transactions

The following sets forth significant related parties and their relationships with the Company:

Company Name		Relationship with the Company
SINA		Parent and affiliates under common control.

Alibaba		Strategic partner and significant shareholder of the Company.

Matching loan between Weibo and SINA.

In January 2017, the Company and its certain subsidiary entered into one-year loan agreements with SINA and SINA subsidiary, pursuant to which the Company is entitled to draw down U.S. dollar-denominated loan from SINA and a SINA subsidiary is entitled to draw down equivalent RMB-denominated loan from the Company’s subsidiary, to facilitate each other’s business operations. All of the loans carried a fixed rate of interest equal to the current market interest rate as of the dates when the principal was drawn down.

For the year ended December 31, 2017, interest income that the Group earned from such RMB-denominated loans to SINA was $1.7 million, and interest expense that the Group paid for such U.S. dollar-denominated loans from SINA was $1.5 million, respectively. As of December 31, 2017, the Company and its subsidiary have settled both loans with SINA and SINA subsidiary with payment of U.S. dollar-denominated principal and interest expense of $61.5 million and receipt of RMB-denominated principal and interest income of $64.0 million, respectively. Besides the matching loans, SINA made an additional $2.0 million short-term loan to Weibo in 2017.

The following sets forth significant related party transactions with the Company:

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Transactions with SINA
Revenue billed through SINA(1)	$	22,114	$	39,285	$	64,093
Costs and expenses allocated from SINA(2)	$	24,678	$	25,703	$	41,136
Interest income on matching loan to SINA	$	—	$	—	$	1,735
Interest expense on matching loan from SINA	$	—	$	—	$	1,537

(1)

For the years ended December 31, 2015, 2016 and 2017, the Group billed $22.1 million, $39.3 million and $64.1 million, respectively, to third parties through SINA.

(2)

Costs and expenses allocated from SINA represented the charges for certain services provided by SINA’s affiliates and charged to the Company using actual cost allocation based on proportional utilization (see Note 1). In addition to the allocated costs and expenses, SINA also billed $29.4 million, $20.3 million, and $22.9 million for other costs and expenses associated with Weibo’s business in 2015, 2016 and 2017, respectively.

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Transactions with Alibaba
Advertising and marketing services provided to Alibaba	$	143,650	$	57,908	$	84,688
Services provided by Alibaba	$	4,515	$	13,988	$	32,734

On April 29, 2013, affiliated entities of SINA, including the Group’s subsidiary, entered into a strategic collaboration with affiliated entities of Alibaba to jointly explore social commerce and develop marketing solutions to enable merchants on Alibaba e-commerce platforms to better connect and build relationships with Weibo users. The strategic collaboration was entered into on a separate agreement from those relating to the investment in Weibo by Alibaba. For the year ended December 31, 2015, the Group recorded $137.4 million advertising and marketing services revenue under the strategic collaboration with Alibaba. The Group has continued to work with Alibaba in the area of social commerce and other areas after the expiration of the strategic collaboration agreement in January 2016. For the years ended December 31, 2016 and 2017, the Group recorded $57.9 million and $84.7 million in advertising and marketing services from Alibaba.

The following sets forth related party outstanding balance:

	As of December 31,
	2016		2017
	(In thousands)
Amount due from SINA(3)	$	18,565	$	16,356
Accounts receivable due from Alibaba	$	24,293	$	42,832

(3)

The Group uses amount due from/to SINA to settle balances arising from cost and expenses allocated from SINA based on proportional utilization, other expenditures associated with the Weibo business paid by SINA and third-party customer and supplier balances settled through SINA.

For the years ended December 31, 2015, 2016 and 2017, advertising and marketing revenues generated from other related parties were $29.2 million, $45.6 million and $71.6 million, respectively, and value-added services revenues from other related parties were $2.1 million, $0.6 million and $21.4 million, respectively. For the years ended December 31, 2015, 2016 and 2017, the Group received promotional services from other related parties amounting to approximately $7.8 million, $10.6 million and $4.1 million, respectively. As of December 31, 2016 and 2017, amount due from other related parties was $30.1 million and $29.7 million, respectively, and accrued and other liabilities due to other related parties were $9.3 million and $5.0 million, respectively.

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2017
Employee Benefit Plans
Employee Benefit Plans	10. Employee Benefit Plans China Contribution Plan The Company’s subsidiaries, VIE and VIE’s subsidiaries in China participate in a government-mandated, multi-employer, defined contribution plan, pursuant to which certain retirement, medical, housing and other welfare benefits are provided to employees. Chinese labor laws require the entities incorporated in China to pay to the local labor and welfare authorities a monthly contribution at a stated contribution rate based on the monthly basic compensation of qualified employees. The local labor bureau is responsible for meeting all retirement benefit obligations. The Group has no further commitments beyond its monthly contribution. For the years ended December 31, 2015, 2016 and 2017, the Group’s total contribution was $29.7 million, $31.4 million and $38.0 million, respectively.

Net Income per Share

12 Months Ended

Dec. 31, 2017

Net Income per Share

Net Income per Share

11. Net Income per Share

Basic net income per share is computed using the weighted average number of the ordinary shares outstanding during the period. Options and RSUs are not considered outstanding in the computation of basic earnings per share (“EPS”). Diluted EPS is computed using the weighted average number of ordinary shares and potential ordinary shares outstanding during the period under the treasury stock method. For the years ended December 31, 2015, 2016 and 2017, options to purchase ordinary shares and RSUs of 9.8 million, 8.1 million and 4.8 million, respectively, were recognized as dilutive factors and included in the calculation of diluted net income per share. For the years ended December 31, 2015, 2016 and 2017, options and RSUs which were anti-dilutive and excluded from the calculation of diluted net income per share were 0.4 million, 0.03 million and nil, respectively. For the year ended December 31, 2017, 1.2 million shares convertible from the convertible debt were anti-dilutive and excluded from the calculation of diluted net income per share.

The following table sets forth the computation of basic and diluted net income per share for the periods indicated:

	Year Ended December 31,
	2015		2016		2017
	(In thousands, except per share data)
Basic net income per share calculation:
Numerator:
Net income attributable to Weibo	$	34,745	$	108,027	$	352,590
Denominator:
Weighted average ordinary shares outstanding	208,163		214,745		220,555
Basic net income per share attributable to Weibo	$	0.17	$	0.50	$	1.60


Diluted net income per share calculation:
Numerator:
Net income attributable for calculating diluted net income per share	$	34,745	$	108,027	$	352,590
Denominator:
Weighted average ordinary shares outstanding	208,163		214,745		220,555
Weighted average ordinary shares equivalents:
Effects of dilutive securities
Stock options	8,572		4,334		1,213
Unvested restricted share units	1,183		3,780		3,595
Shares used in computing diluted net income per share attributable to Weibo	217,918		222,859		225,363
Diluted net income per share attributable to Weibo	$	0.16	$	0.48	$	1.56

Segment Information

12 Months Ended

Dec. 31, 2017

Segment Information

Segment Information

12. Segment Information

The Group currently operates and manages its business in two principal business segments globally—advertising and marketing services and value-added services. Information regarding the business segments provided to the Group’s chief operating decision makers (“CODM”), its Chief Executive Officer, is at the revenue level and the Group currently does not allocate operating costs or assets to its segments, as its CODM does not use such information to allocate resources or evaluate the performance of the operating segments. As substantially all of the Group’s revenues are derived from within the PRC and substantially all of the Group’s long-lived assets are located within the PRC, no geographical information is presented.

The following is a summary of the Group’s revenues:

Revenues	Advertising & Marketing		Value-added services		Total
	(In thousand)

Year ended December 31, 2015	$	402,415	$	75,476	$	477,891

Year ended December 31, 2016	$	570,982	$	84,818	$	655,800

Year ended December 31, 2017	$	996,745	$	153,309	$	1,150,054

Profit Appropriation and Restricted Net Assets	12 Months Ended
Profit Appropriation and Restricted Net Assets	Dec. 31, 2017
Profit Appropriation and Restricted Net Assets
Profit Appropriation and Restricted Net Assets	13. Profit Appropriation and Restricted Net Assets The Company’s subsidiaries, VIE and VIE’s subsidiaries in China are required to make appropriations to certain non-distributable reserve funds. In accordance with the laws applicable to China’s WFOE, its subsidiaries have to make appropriations from their after-tax profit (as determined under Generally Accepted Accounting Principles in the PRC (“PRC GAAP”) to non-distributable reserve funds including (i) general reserve fund, (ii) enterprise expansion fund and (iii) staff bonus and welfare fund. General reserve fund is at least 10% of the after-tax profits calculated in accordance with the PRC GAAP. Appropriation is not required if the reserve fund has reached 50% of the registered capital of the respective company. The appropriation of the other two reserve funds is at the Group’s discretion. At the same time, the Company’s VIE, in accordance with the China Company Laws, must make appropriations from their after-tax profit (as determined under the PRC GAAP) to non-distributable reserve funds including (i) statutory surplus fund, and (ii) discretionary surplus fund. Statutory surplus fund is at least 10% of the after-tax profits calculated in accordance with the PRC GAAP. Appropriation is not required if the reserve fund has reached 50% of the registered capital of the respective company. General reserve fund and statutory surplus fund are restricted for set off against losses, expansion of production and operation or increase in registered capital of the respective company. These reserves are not transferable to the Company in the form of cash dividends, loans or advances. These reserves are therefore not available for distribution except in liquidation. As of December 31, 2016 and 2017, the Group accrued approximately $28.0 million and $73.6 million in the reserve fund. Under the PRC laws and regulations, the subsidiaries, VIE and VIE’s subsidiaries incorporated in the PRC are restricted in their ability to transfer a portion of their net assets to the Group either in the form of dividends, loans or advances of the consolidated net assets. Even though the Group currently does not require any such dividends, loans or advances from the PRC subsidiaries, VIE and VIE’s subsidiaries for working capital and other funding purposes, the Group may in the future require additional cash resources from the PRC subsidiaries, VIE and VIE’s subsidiaries due to changes in business conditions, to fund future acquisitions and development, or merely declare and pay dividends to or distribution to its shareholders. Net assets subject to restriction for the Group amounted to $334.8 million, or 28.1% of the Group’s total consolidated net assets as of December 31, 2017.

Financial Instruments

12 Months Ended

Dec. 31, 2017

Financial Instruments

Financial Instruments

14. Financial Instruments

Fair Value

The following table sets forth the financial instruments measured at fair value by level within the fair value hierarchy as of December 31, 2016 and 2017:

	Fair Value Measurements
	(in thousands)
	Total		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of December 31, 2016:
Bank time deposits*	$	31,188	$	—	$	31,188	$	—
Available-for-sale securities**	5,274		5,274		—		—

Total	$	36,462	$	5,274	$	31,188	$	—


As of December 31, 2017:
Bank time deposits*	$	791,730	$	—	$	791,730	$	—
Available-for-sale securities**	4,279		4,279		—		—

Total	$	796,009	$	4,279	$	791,730	$	—

* Included in short-term investments on the Group’s consolidated balance sheets.

** Included in long-term investments on the Group’s consolidated balance sheets.

Recurring

The Group measures bank time deposits and available-for-sale securities at fair value on a recurring basis.

The fair value of the Group’s available-for-sale securities are determined based on the quoted market price (Level 1). The fair value of the Group’s bank time deposits are determined based on the quoted market price for similar products (Level 2).

The Group reviews its available-for-sale investments regularly to determine if an investment is other-than-temporarily impaired due to changes in quoted market price or other impairment indicators. For the years ended December 31, 2015, 2016 and 2017, impairment related to available-for-sale securities was nil, $4.8 million and nil, respectively (see Note 4 for further information).

Non-recurring

The Group measures certain financial assets, including investments under the cost method and equity method, at fair value on a non-recurring basis only if an impairment charge is recognized.

The fair value of the Group’s privately held investments are determined using the income approach with unobservable inputs, such as the investee company’s historical financial results and assumptions about future growth rates, which require significant judgment to determine, and the market approach based on market participants’ price quote for the investment. As of December 31, 2016 and 2017, certain privately held investments under the cost method and equity method were measured using significant unobservable inputs (Level 3) and written down from their respective carrying value to a fair value of nil, with impairment charges incurred and recorded in earnings for the year then ended. The impairment charges related to these investments were $8.0 million, $35.4 million and $4.7 million for the years ended December 31, 2015, 2016 and 2017, respectively, (see Note 4 for further information). The fair value of the privately held investments was measured based on discounted cash flow with unobservable inputs including the discount curve of market interest rates, which ranged from 20% to 22%.

The Group’s non-financial assets, such as intangible assets, goodwill and fixed assets, are measured at fair value only if they were determined to be impaired. In accordance with the Group’s policy to perform an impairment assessment of its goodwill on an annual basis as of the balance sheet date or when facts and circumstances warrant a review, the Group performed an impairment assessment on its goodwill by reporting unit annually. The Group concluded that no write-down was warranted for the years ended December 31, 2015, 2016 and 2017, respectively.

Convertible Debt	12 Months Ended
Convertible Debt	Dec. 31, 2017
Convertible Debt
Convertible Debt	15. Convertible Debt In October 2017, the Company issued $900 million in aggregate principal amount of 1.25% coupon interest convertible senior notes due on November 15, 2022 (“2022 Notes”) at par. The Notes may be converted into Weibo’s American depositary shares (“ADSs”), each representing one Class A ordinary share of the Company, at the option of the holders, which is equivalent to an initial conversion price of approximately US$133.27 per ADS, subject to adjustment. The conversion rate may be adjusted under certain circumstances, such as distribution of dividends and stock splits. In addition, upon a make-whole fundamental change prior to the maturity date of the notes, the Company will, under certain circumstances, increase the applicable conversion rate for a holder that elects to convert its notes in connection with such make-whole fundamental change. The net proceeds to the Company from the issuance of the 2022 Notes were $879.3 million, net of issuance cost of $20.7 million. The Company will pay cash interest at an annual rate of 1.25% on the 2022 Notes, payable semiannually in arrears in cash on May 15 and November 15 of each year, beginning May 15, 2018. The issuance costs of the 2022 Notes are being amortized to interest expense over the contractual life.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies

Commitments and Contingencies

16. Commitments and Contingencies

Operating lease commitments include the commitments under the lease agreements for the Group’s office premises. The Group leases its office facilities under non-cancelable operating leases with various expiration dates through 2022. For the years ended December 31, 2015, 2016 and 2017, lease expense was $15.5 million, $14.4 million and $9.2 million, respectively. Based on the current rental lease agreements, future minimum lease payments commitments as of December 31, 2017 were as follows:

Operating lease commitments	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	34,005	$	8,792	$	17,011	$	8,202	$	—

Purchase commitments mainly include minimum commitments for internet connection and marketing activities.

Purchase commitments as of December 31, 2017 were as follows:

Purchase commitments	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	384,621	$	366,939	$	17,627	$	55	$	—

2022 Notes represents future maximum commitment relating to the principal amount and interests in connection with the issuance of $900 million in aggregate principal amount of 1.25% coupon interest convertible senior notes, which will mature on November 15, 2022.

2022 Notes	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	956,750	$	13,219	$	22,500	$	921,031	$	—

There are uncertainties regarding the legal basis of the Group’s ability to operate an Internet business in China. Although China has implemented a wide range of market-oriented economic reforms, the telecommunication, information and media industries remain highly regulated. Not only are such restrictions currently in place, the existing regulations are unclear as to which specific segments of these industries companies with foreign investors, including the Company, may operate. Therefore, the Group may be required to limit the scope of its operations in China, and this could have a material adverse effect on its financial position, results of operations and cash flows.

In June and August 2017, the Company and certain of its current and former directors and officers were named as defendants in two putative securities class actions filed in the United States District Court for the District of New Jersey, respectively. The actions - purportedly brought on behalf of a class of persons who allegedly suffered damages as a result of their trading in the Company’s ADSs between April 27 and June 22, 2017 or between April 28, 2016 and June 19, 2017, allege that the Company’s public filings contained material misstatements and omissions in violation of the U.S. federal securities laws. On September 28, 2017, the court entered an order appointing a lead plaintiff and consolidating the two cases. On November 27, 2017, the lead plaintiff filed a consolidated class action complaint. On January 26, 2018, the Company and one individual defendant filed a motion to dismiss the amended complaint, which motion is currently pending before the court. The action remains in its preliminary stages. As of this stage, the Company is unable to estimate the possible outcome or loss or possible range of loss, if any, associated with the resolution of these lawsuits. As of December 31, 2017, no losses with respect to this contingency were accrued.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events
Subsequent Events	17. Subsequent Events The Group has performed an evaluation of subsequent events through the date of this report, which is the date the financial statements were issued, with no other material events nor transactions needing recognition or disclosure found.

Additional Information-Condensed Financial Statements of Weibo Corporation

12 Months Ended

Dec. 31, 2017

Additional Information-Condensed Financial Statements of Weibo Corporation

Additional Information-Condensed Financial Statements of Weibo Corporation

18. Additional Information—Condensed Financial Statements of Weibo Corporation

The condensed financial information of Weibo Corporation has been prepared in accordance with SEC Regulation S-X Rule 5-04 and Rule 12-04, using the same accounting policies as set out in the Group’s consolidated financial statements, except that the Company used equity method to account for the investment in its subsidiaries, VIE and VIE’s subsidiaries.

The operations of the Company, its subsidiaries, VIE and VIE’s subsidiaries were included in the consolidated financial statements, whereby the inter-company balances and transactions were eliminated upon consolidation. For the purpose of the Company’s stand-alone financial information, its investment in subsidiaries, VIE and VIE’s subsidiaries were reported using equity method of accounting.

Relevant PRC statutory laws and regulations permit the payment of dividends by the Company’s PRC subsidiaries and VIE only out of their retained earnings, if any, as determined in accordance with PRC accounting standards and regulations. In addition, PRC laws and regulations require that annual appropriations of 10% of after-tax income should be set aside as a reserve prior to the payment of dividends. As a result of these PRC laws and regulations, the Company’s PRC subsidiaries and VIE are restricted in their ability to transfer a portion of their net assets to the Company, either in the form of dividends, loans or advances.

The footnote disclosures contain supplemental information relating to the operations of the Company and, as such, these statements should be read in conjunction with the notes to the consolidated financial statements of the Group. Certain information and footnote disclosures normally included in financial statements prepared in accordance with US GAAP have been condensed or omitted.

As of December 31, 2016 and 2017, there were no material contingencies, significant provisions for long-term obligations, or guarantees of the Group, except for those which have been separately disclosed in the consolidated financial statements, if any.

Condensed Financial Information of Weibo Corporation

Balance Sheets

(In thousands, except for par value)

	As of December 31,
	2016			2017

ASSETS
Current assets:
Cash and cash equivalents	$	7,235		$	113,783
Short-term investments	30,401			782,530
Prepaid expenses and other current assets	5,682			5,579


Total current assets	43,318			901,892
Long-term investments	349,502			376,579
Investment in subsidiaries, VIE and VIE’s subsidiaries	367,114			808,150
Amount due from SINA	89			—


Total assets	$	760,023		$	2,086,621


LIABILITIES AND SHAREHOLDERS’ EQUITY
Accrued and other liabilities	$	6,132		$	13,765
Convertible debt	—			879,983
Long-term Liabilities	666			286


Total liabilities	$	6,798		$	894,034


Commitments and contingencies

Shareholders’ equity:
Shareholders’ equity:
Ordinary shares: $0.00025 par value; 2,400,000 and 2,400,000 shares (including 1,800,000 Class A ordinary shares, 200,000 Class B ordinary shares and 400,000 shares to be designated)authorized; 218,076 and 222,706 shares (including 120,927 Class A ordinary shares and 101,779 Class B ordinary shares) issued and outstanding as of December 31, 2016 and 2017, respectively.	$	55		$	56
Additional paid-in capital	979,805			1,030,048
Accumulated other comprehensive income (loss)	(26,994		)	9,534
Retained earnings (Accumulated deficit)	(199,641		)	152,949


Total shareholders’ equity	753,225			1,192,587


Total liabilities and shareholders’ equity	$	760,023		$	2,086,621

Condensed Financial Information of Weibo Corporation

Statements of Comprehensive Income

(In thousands)

	Year Ended December 31,
	2015			2016			2017

Operating loss	$	(1,279	)	$	(1,891	)	$	(945	)
Interest and other income (expenses), net	4,759			1,763			(1,941		)
Investment related impairment	—			(23,822		)	—
Share of income of subsidiaries, VIE, and VIE’s subsidiaries	31,265			131,977			355,476


Net income attributable to Weibo	34,745			108,027			352,590


Other comprehensive income (loss)
Currency translation adjustments (net of tax of nil, nil, and nil for 2015, 2016 and 2017, respectively)	(7,601		)	(18,624		)	37,523
Available-for-sale securities:
Change in unrealized loss from available-for-sale securities (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	(198		)	(2,557		)	(995		)
Reclassification adjustment for net loss included in net income (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	—			4,822			—

Net change, net of tax	(198		)	2,265			(995		)


Total comprehensive income	$	26,946		$	91,668		$	389,118

Condensed Financial Information of Weibo Corporation

Statements of Cash flow

(In thousands)

	2015			2016			2017

Net cash provided by operating activities	$	5,317		$	1,025		$	3,996

Purchase of short-term investments	(148,863		)	(30,046		)	(781,000		)
Maturity of short-term investments	218,762			97,798			30,046
Investments and prepayments on equity investments	(247,200		)	(120,000		)	(28,072		)
Investment in subsidiaries	(4,978		)	(6,535		)	—

Net cash used in investing activities	(182,279		)	(58,783		)	(779,026		)

Proceeds from convertible debt, net of debt issuance costs	—			—			879,293
Proceeds from employees options exercised	7,822			4,183			2,285
Loan from SINA	—			—			60,000
Repayment of loan from SINA	—			—			(60,000		)

Net cash provided by financing activities	7,822			4,183			881,578


Net increase (decrease) in cash and cash equivalents	$	(169,140	)	$	(53,575	)	$	106,548


Cash and cash equivalents at the beginning of year	$	229,950		$	60,810		$	7,235
Cash and cash equivalents at the end of year	$	60,810		$	7,235		$	113,783
Supplemental schedule of non-cash investing and financing activities
Investment in subsidiaries and VIE directly financed by SINA	$	17,582		$	18,277		$	—

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

+ References + Details

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Significant Accounting Policies

Basis of presentation

Use of estimates

Revenue recognition

Advertising and marketing revenues

Value-added services revenues

Cost of revenues

Sales and Marketing Expenses

Product development expenses

Stock-based compensation

Taxation

Income taxes

Operating leases

Cash equivalents

Accounts receivable and allowances for doubtful accounts

Fair value measurements

Financial instruments

Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities.

Level 3 applies to asset or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.

Long-term investments

Business combination

Long-lived assets

Property and equipment

Goodwill

Intangible assets other than goodwill

Convertible debt

Deferred revenues

Non-controlling interests

Foreign currency

Net Income per share

Segment reporting

Concentration of risks

Recent accounting pronouncements

Operations and reorganization (Tables)

12 Months Ended

Dec. 31, 2017

Operations and reorganization

Schedule of the Company's major subsidiaries, VIE and VIE's subsidiary

Company	Date of Incorporation	Place of Incorporation	Percentage of Direct/ Indirect Economic Interest
Major Subsidiaries
Weibo Hong Kong Limited (“Weibo HK”)	July 19, 2010	Hong Kong	100	%

Weibo Internet Technology (China) Co., Ltd. (“Weibo Technology” or “the WFOE”)	October 11, 2010	PRC	100	%

Major VIE and VIE’s subsidiary
Beijing Weimeng Technology Co., Ltd (“Weimeng”)	August 9, 2010	PRC	100	%

Beijing Weibo Interactive Internet Technology Co., Ltd. (‘‘Weibo Interactive’’)	Acquired in May 2013	PRC	100	%

Schedule of total cost and expenses allocated from SINA

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Cost of revenues	$	6,550	$	11,022	$	13,699
Sales and marketing	1,263		1,271		9,732
Product development	12,981		9,094		11,312
General and administrative	3,884		4,316		6,393

	$	24,678	$	25,703	$	41,136

Schedule of assets, liabilities, results of operations and cash flows of the VIE and the VIE's subsidiaries taken as a whole.

	As of December 31,
	2016		2017
	(In thousands)
Cash, cash equivalents and short-term Investments	$	57,505	$	40,458
Accounts receivable	115,338		166,212
Property and equipment, net	357		146
Intangible assets	1,100		517
Goodwill	9,969		13,123
Prepayment for long-term investments	144		4,967
Long-term investments	49,195		74,935
Deferred tax assets	2,312		4,772
Amount due from SINA	12,163		4,677
Others	28,247		28,850

Total assets	$	276,330	$	338,657


Accounts payable	$	25,850	$	32,444
Accrued and other liabilities	64,879		114,239
Deferred revenues	38,313		54,651
Income tax payable	8,214		16,268
Amount due to the subsidiaries of the Group	171,460		57,639
Deferred tax liability	274		129

Total liabilities	$	308,990	$	275,370

	Year Ended December 31,
	2015			2016			2017
	(In thousands)
Net revenues	$	391,568		$	530,598		$	906,129
Net income (loss)	$	(10,572	)	$	(21,758	)	$	21,252

	Year Ended December 31,
	2015			2016			2017
	(In thousands)
Net cash provided by (used in) operating activities	$	158,290		$	(42,556	)	$	(66,972	)
Net cash used in investing activities	$	(39,965	)	$	(28,577	)	$	(34,720	)
Net cash provided by (used in) financing activities	$	—		$	(1,148	)	$	76,232

Net increase (decrease) in cash and cash equivalents	$	118,325		$	(72,281	)	$	(25,460	)

- Definition

Tabular disclosure of the significant judgments and assumptions made in determining whether a variable interest (as defined) held by the entity requires the variable interest entity (VIE) (as defined) to be consolidated and (or) disclose information about its involvement with the VIE, individually or in aggregate (as applicable); the nature of restrictions, if any, on the consolidated VIE's assets and on the settlement of its liabilities reported by an entity in its statement of financial position, including the carrying amounts of such assets and liabilities; the nature of, and changes in, the risks associated with involvement in the VIE; how involvement with the VIE affects the entity's financial position, financial performance, and cash flows; the lack of recourse if creditors (or beneficial interest holders) of the consolidated VIE have no recourse to the general credit of the primary beneficiary (if applicable); the terms of arrangements, giving consideration to both explicit arrangements and implicit variable interests, if any, that could require the entity to provide financial support to the VIE, including events or circumstances that could expose the entity to a loss; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; the significant factors considered and judgments made in determining that the power to direct the activities of a VIE that most significantly impact the VIE's economic performance are shared (as defined); the carrying amounts and classification of assets and liabilities of the VIE included in the statement of financial position; the entity's maximum exposure to loss, if any, as a result of its involvement with the VIE, including how the maximum exposure is determined and significant sources of the entity's exposure to the VIE; a comparison of the carrying amounts of the assets and liabilities and the entity's maximum exposure to loss; information about any liquidity arrangements, guarantees, and (or) other commitments by third parties that may affect the fair value or risk of the entity's variable interest in the VIE; whether or not the entity has provided financial support or other support (explicitly or implicitly) to the VIE that it was not previously contractually required to provide or whether the entity intends to provide that support, including the type and amount of the support and the primary reasons for providing the support; and supplemental information the entity determines necessary to provide.

+ References + Details

Cash, Cash Equivalents and Short-term Investments (Tables)

12 Months Ended

Dec. 31, 2017

Cash, Cash Equivalents and Short-term Investments

Schedule of cash, cash equivalents and short-term investments

	As of December 31,
	2016		2017
	(In thousands)
Cash and cash equivalents:
Cash	$	364,766	$	1,000,953


Short-term investments:
Bank time deposits	31,188		791,730


Total cash, cash equivalents and short-term investments	$	395,954	$	1,792,683

Long-term Investments (Tables)

12 Months Ended

Dec. 31, 2017

Long-term Investments

Schedule of changes in the Group's long-term investments

	Cost Method			Equity Method			Available-for-Sale Securities			Total
	(In thousands)

Balance at December 31, 2014	$	50,594		$	154		$	13,029		$	63,777
Investments made	252,256			—			—			252,256
Loss from equity method investment	—			(6		)	—			(6		)
Disposal of investments	(13,134		)	—			—			(13,134		)
Impairment on investments	(6,608		)	—			—			(6,608		)
Unrealized loss	—			—			(198		)	(198		)
Currency translation adjustment	(1,401		)	(7		)	—			(1,408		)


Balance at December 31, 2015	$	281,707		$	141		$	12,831		$	294,679
Investments made	147,767			4,324			—			152,091
Loss from equity method investment	—			(130		)	—			(130		)
Disposal of investments	(6,010		)	—			(5,000		)	(11,010		)
Impairment on investments	(31,586		)	—			—			(31,586		)
Unrealized loss	—			—			(2,557		)	(2,557		)
Currency translation adjustment	(1,548		)	(6		)	—			(1,554		)


Balance at December 31, 2016	$	390,330		$	4,329		$	5,274		$	399,933
Investments made	31,776			22,307			—			54,083
Gain from equity method investment	—			1,030			—			1,030
Dividend received from equity method investment	—			(267		)	—			(267		)
Impairment on investments	(4,747		)	—			—			(4,747		)
Unrealized loss	—			—			(995		)	(995		)
Currency translation adjustment	2,997			303			—			3,300


Balance at December 31, 2017	$	420,356		$	27,702		$	4,279		$	452,337

Acquisitions (Tables)

12 Months Ended

Dec. 31, 2017

Acquisitions

Schedule of the changes in the Group's goodwill by segment

	Advertising & Marketing		Other			Total
	(In thousands)
Balance as of December 31, 2015	$	—	$	11,117		$	11,117
Currency translation adjustment	—		(851		)	(851		)

Balance as of December 31, 2016	$	—	$	10,266		$	10,266

New acquisition	—		2,318			2,318
Currency translation adjustment	—		836			836

Balance as of December 31, 2017	$	—	$	13,420		$	13,420

Schedule of estimated amortization expenses

Year Ended December 31,	(In thousands)
2018	$	517
2019 and thereafter	—

Total expected amortization expense	$	517

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Stock-Based Compensation

Schedule of the stock-based compensation

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Cost of revenues	$	1,196	$	2,616	$	3,716
Sales and marketing	3,209		5,357		8,264
Product development	10,210		15,076		21,879
General and administrative	11,784		13,853		14,178

	$	26,399	$	36,902	$	48,037

Summary of the number of shares available for issuance

	Shares Available
	(In thousands)
December 31, 2014	2,738
Addition	21,684
Granted*	(4,851	)
Cancelled/expired/forfeited	646


December 31, 2015	20,217
Addition	—
Granted*	(1,917	)
Cancelled/expired/forfeited	578


December 31, 2016	18,878
Addition	—
Granted*	(736	)
Cancelled/expired/forfeited	398


December 31, 2017	18,540

Summary of option activities under the Company' stock option program

	Options Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
	(In thousands)				(In years)	(In thousands)
December 31, 2014	14,330		$	1.28	3.2	$	185,684
Granted	—		$	—
Exercised	(7,309	)	$	1.11
Cancelled/expired/forfeited	(718	)	$	3.22


December 31, 2015	6,303		$	1.26	2.4	$	114,975
Granted	—		$	—
Exercised	(3,625	)	$	1.10
Cancelled/expired/forfeited	(91	)	$	3.37


December 31, 2016	2,587		$	1.41	1.6	$	101,403
Granted	—		$	—
Exercised	(2,122	)	$	1.04
Cancelled/expired/forfeited	(28	)	$	0.68


December 31, 2017	437		$	3.24	2.0	$	43,800


Vested and expected to vest as of December 31, 2016	2,572		$	1.40	1.6	$	100,819
Exercisable as of December 31, 2016	2,433		$	1.28	1.4	$	95,678

Vested and expected to vest as of December 31, 2017	437		$	3.24	2.0	$	43,800
Exercisable as of December 31, 2017	437		$	3.24	2.0	$	43,800

Schedule of stock options outstanding

Range of Exercise Prices	Options Outstanding	Weighted Average Exercise Price		Options Exercisable	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
	(In thousands)			(In thousands)			(In years)
As of December 31, 2016
$ 0.36 - $0.41	1,639	$	0.36	1,639	$	0.36	0.7
$ 0.96 - $1.80	79	$	0.97	79	$	0.97	1.2
$ 3.25 - $3.36	341	$	3.33	338	$	3.33	2.5
$ 3.43 - $3.50	528	$	3.48	377	$	3.48	3.7

	2,587	$	1.41	2,433	$	1.28	1.6


As of December 31, 2017
$ 0.96 - $1.80	31	$	0.97	31	$	0.97	0.2
$ 3.25 - $3.36	179	$	3.33	179	$	3.33	1.4
$ 3.43 - $3.50	227	$	3.48	227	$	3.48	2.6

	437	$	3.24	437	$	3.24	2.0

Performance-Based Restricted Share Units

Stock-Based Compensation

Summary of restricted share unit activities

	Shares Granted		Weighted-Average Grant Date Fair Value
	(In thousands)
December 31, 2015	—		$	—
Awarded	111		$	27.00
Cancelled	(3	)	$	27.00


December 31, 2016	108		$	27.00
Awarded	155		$	50.45
Vested	(102	)	$	27.00
Cancelled	(32	)	$	46.42


December 31, 2017	129		$	50.32

Service-Based Restricted share Units

Stock-Based Compensation

Summary of restricted share unit activities

	Shares Granted		Weighted- Average Grant Date Fair Value
	(In thousands)
December 31, 2014	3,507		$	16.44
Awarded	4,851		$	12.41
Vested	(1,211	)	$	14.69
Cancelled	(646	)	$	14.18


December 31, 2015	6,501		$	13.98
Awarded	1,806		$	24.94
Vested	(2,274	)	$	14.73
Cancelled	(575	)	$	14.58


December 31, 2016	5,458		$	17.23
Awarded	581		$	62.87
Vested	(2,406	)	$	17.01
Cancelled	(366	)	$	17.72


December 31, 2017	3,267		$	25.45

Other Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2017

Other Balance Sheet Components

Schedule of other balance sheet components

	As of December 31,
	2015		2016			2017
	(In thousands)
Accounts receivable, net:
Due from third parties			$	66,701		$	105,686
Due from Alibaba			24,293			42,832
Due from other related parties			31,589			29,696


Total gross amount			$	122,583		$	178,214
Allowance for doubtful accounts:
Balance at the beginning of the year	(2,440	)	(1,375		)	(6,529		)
Reversal (additional provision) charged to expenses, net	368		(7,787		)	(5,478		)
Write-off	697		2,633			3,893


Balance at the end of the year	(1,375	)	(6,529		)	(8,114		)

			$	116,054		$	170,100


Prepaid expenses and other current assets:
Rental and other deposits			$	3,965		$	2,233
Prepayment for investments			24,953			20,881
Advertising prepayment			5,267			3,959
Prepayment to outsourced service providers			4,043			5,369
Amounts deposited by users*			21,203			25,277
Content fees			2,111			7,393
Others			5,122			4,121

			$	66,664		$	69,233


Property and equipment, net:
Computers and equipment			$	94,170		$	113,558
Leasehold improvements			2,054			4,321
Furniture and fixtures			922			1,241
Others			1,655			2,574


Property and equipment, gross			98,801			121,694
Less: Accumulated depreciation			(75,985		)	(87,901		)

			$	22,816		$	33,793


Accrued and other liabilities**:
Payroll and welfare			$	33,786		$	57,848
Marketing expenses			40,968			53,380
Payroll withholding taxes			3,547			3,547
Sales rebates			31,598			60,663
Professional fees			4,255			6,170
VAT and other tax payable			35,728			51,563
Payable to other service providers			1,457			362
Amounts due to users*			21,203			25,277
Others			7,600			9,805

			$	180,142		$	268,615

** Include amounts due to third parties, employees, related parties (see Note 9) and Weibo wallet users.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of income before income taxes

	Year Ended December 31,
	2015			2016			2017
	(In thousands, except percentage)
Income before income tax expenses	$	36,780		$	109,980		$	417,111
Loss from non-China operations	$	(28,016	)	$	(60,193	)	$	(52,261	)
Income from China operations	$	64,796		$	170,173		$	469,372
Income tax expense applicable to China operations	$	2,591		$	4,316		$	66,746
Effective tax rate for China operations	4.0		%	2.5		%	14.2		%

Schedule of current and deferred portion of income tax expenses (benefits)

	Years Ended December 31,
	2015			2016			2017
	(In thousands)
Deferred tax benefits	$	(977	)	$	(4,630	)	$	(1,503	)
Current income tax expenses	3,568			8,946			68,249


Income tax expenses	$	2,591		$	4,316		$	66,746

Schedule of reconciliation between the statutory EIT rate and the effective tax rate for China operations

	Year Ended December 31,
	2015		2016		2017
Statutory EIT rate	25.0	%	25.0	%	25.0	%
Effect on tax holiday and preferential tax treatment	(24.2	) %	(29.6	)%	(11.6	)%
Permanent differences	0.5	%	1.2	%	0.2	%
Change in valuation allowance	2.7	%	5.9	%	0.6	%


Effective tax rate for China operations	4.0	%	2.5	%	14.2	%

Schedule of significant components of deferred tax assets and liabilities for China operations

	As of December 31,
	2016			2017
	(In thousands)
Deferred tax assets:
Net operating loss carry forwards	$	32,158		$	10,280
Less: valuation allowance	(32,158		)	(10,280		)
Depreciation, accounts receivable, accrued and other liabilities	13,957			19,931
Less: valuation allowance	(8,576		)	(11,629		)


Net deferred tax assets (included in other assets)	$	5,381		$	8,302


Deferred tax liabilities:
Acquired intangible assets	$	274		$	129
Depreciation	362			527
Others	181			1,224


Total deferred tax liabilities	$	817		$	1,880

Related Party Transactions (Tables)

12 Months Ended

Dec. 31, 2017

Related Party Transactions

Schedule of significant related parties and their relationships with the Company

Company Name		Relationship with the Company
SINA		Parent and affiliates under common control.

Alibaba		Strategic partner and significant shareholder of the Company.

Schedule of significant related party transactions with the Company

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Transactions with SINA
Revenue billed through SINA(1)	$	22,114	$	39,285	$	64,093
Costs and expenses allocated from SINA(2)	$	24,678	$	25,703	$	41,136
Interest income on matching loan to SINA	$	—	$	—	$	1,735
Interest expense on matching loan from SINA	$	—	$	—	$	1,537

(1)

For the years ended December 31, 2015, 2016 and 2017, the Group billed $22.1 million, $39.3 million and $64.1 million, respectively, to third parties through SINA.

(2)

	Year Ended December 31,
	2015		2016		2017
	(In thousands)
Transactions with Alibaba
Advertising and marketing services provided to Alibaba	$	143,650	$	57,908	$	84,688
Services provided by Alibaba	$	4,515	$	13,988	$	32,734

	As of December 31,
	2016		2017
	(In thousands)
Amount due from SINA(3)	$	18,565	$	16,356
Accounts receivable due from Alibaba	$	24,293	$	42,832

(3)

Net Income per Share (Tables)

12 Months Ended

Dec. 31, 2017

Net Income per Share

Schedule of basic and diluted net income per share

	Year Ended December 31,
	2015		2016		2017
	(In thousands, except per share data)
Basic net income per share calculation:
Numerator:
Net income attributable to Weibo	$	34,745	$	108,027	$	352,590
Denominator:
Weighted average ordinary shares outstanding	208,163		214,745		220,555
Basic net income per share attributable to Weibo	$	0.17	$	0.50	$	1.60


Diluted net income per share calculation:
Numerator:
Net income attributable for calculating diluted net income per share	$	34,745	$	108,027	$	352,590
Denominator:
Weighted average ordinary shares outstanding	208,163		214,745		220,555
Weighted average ordinary shares equivalents:
Effects of dilutive securities
Stock options	8,572		4,334		1,213
Unvested restricted share units	1,183		3,780		3,595
Shares used in computing diluted net income per share attributable to Weibo	217,918		222,859		225,363
Diluted net income per share attributable to Weibo	$	0.16	$	0.48	$	1.56

Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Information

Summary of the Group's revenues

Revenues	Advertising & Marketing		Value-added services		Total
	(In thousand)

Year ended December 31, 2015	$	402,415	$	75,476	$	477,891

Year ended December 31, 2016	$	570,982	$	84,818	$	655,800

Year ended December 31, 2017	$	996,745	$	153,309	$	1,150,054

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Financial Instruments

Schedule of financial instruments measured at fair value by level within the fair value hierarchy

	Fair Value Measurements
	(in thousands)
	Total		Quoted Prices in Active Market for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of December 31, 2016:
Bank time deposits*	$	31,188	$	—	$	31,188	$	—
Available-for-sale securities**	5,274		5,274		—		—

Total	$	36,462	$	5,274	$	31,188	$	—


As of December 31, 2017:
Bank time deposits*	$	791,730	$	—	$	791,730	$	—
Available-for-sale securities**	4,279		4,279		—		—

Total	$	796,009	$	4,279	$	791,730	$	—

* Included in short-term investments on the Group’s consolidated balance sheets.

** Included in long-term investments on the Group’s consolidated balance sheets.

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies

Schedule of future minimum lease payments

Operating lease commitments	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	34,005	$	8,792	$	17,011	$	8,202	$	—

Schedule of purchase commitments

Purchase commitments	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	384,621	$	366,939	$	17,627	$	55	$	—

Schedule of Notes 2022 maturity

2022 Notes	Total		Less than One Year		One to Three Years		Three to Five Years		More than Five Years
	(In thousands)
As of December 31, 2017:	$	956,750	$	13,219	$	22,500	$	921,031	$	—

Additional Information-Condensed Financial Statements of Weibo Corporation (Tables) - Weibo Corporation

12 Months Ended

Dec. 31, 2017

Balance sheets

Balance Sheets

(In thousands, except for par value)

	As of December 31,
	2016			2017

ASSETS
Current assets:
Cash and cash equivalents	$	7,235		$	113,783
Short-term investments	30,401			782,530
Prepaid expenses and other current assets	5,682			5,579


Total current assets	43,318			901,892
Long-term investments	349,502			376,579
Investment in subsidiaries, VIE and VIE’s subsidiaries	367,114			808,150
Amount due from SINA	89			—


Total assets	$	760,023		$	2,086,621


LIABILITIES AND SHAREHOLDERS’ EQUITY
Accrued and other liabilities	$	6,132		$	13,765
Convertible debt	—			879,983
Long-term Liabilities	666			286


Total liabilities	$	6,798		$	894,034


Commitments and contingencies

Shareholders’ equity:
Shareholders’ equity:
Ordinary shares: $0.00025 par value; 2,400,000 and 2,400,000 shares (including 1,800,000 Class A ordinary shares, 200,000 Class B ordinary shares and 400,000 shares to be designated)authorized; 218,076 and 222,706 shares (including 120,927 Class A ordinary shares and 101,779 Class B ordinary shares) issued and outstanding as of December 31, 2016 and 2017, respectively.	$	55		$	56
Additional paid-in capital	979,805			1,030,048
Accumulated other comprehensive income (loss)	(26,994		)	9,534
Retained earnings (Accumulated deficit)	(199,641		)	152,949


Total shareholders’ equity	753,225			1,192,587


Total liabilities and shareholders’ equity	$	760,023		$	2,086,621

Statements of Comprehensive Income

(In thousands)

	Year Ended December 31,
	2015			2016			2017

Operating loss	$	(1,279	)	$	(1,891	)	$	(945	)
Interest and other income (expenses), net	4,759			1,763			(1,941		)
Investment related impairment	—			(23,822		)	—
Share of income of subsidiaries, VIE, and VIE’s subsidiaries	31,265			131,977			355,476


Net income attributable to Weibo	34,745			108,027			352,590


Other comprehensive income (loss)
Currency translation adjustments (net of tax of nil, nil, and nil for 2015, 2016 and 2017, respectively)	(7,601		)	(18,624		)	37,523
Available-for-sale securities:
Change in unrealized loss from available-for-sale securities (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	(198		)	(2,557		)	(995		)
Reclassification adjustment for net loss included in net income (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	—			4,822			—

Net change, net of tax	(198		)	2,265			(995		)


Total comprehensive income	$	26,946		$	91,668		$	389,118

Statements of Cash flow

(In thousands)

	2015			2016			2017

Net cash provided by operating activities	$	5,317		$	1,025		$	3,996

Purchase of short-term investments	(148,863		)	(30,046		)	(781,000		)
Maturity of short-term investments	218,762			97,798			30,046
Investments and prepayments on equity investments	(247,200		)	(120,000		)	(28,072		)
Investment in subsidiaries	(4,978		)	(6,535		)	—

Net cash used in investing activities	(182,279		)	(58,783		)	(779,026		)

Proceeds from convertible debt, net of debt issuance costs	—			—			879,293
Proceeds from employees options exercised	7,822			4,183			2,285
Loan from SINA	—			—			60,000
Repayment of loan from SINA	—			—			(60,000		)

Net cash provided by financing activities	7,822			4,183			881,578


Net increase (decrease) in cash and cash equivalents	$	(169,140	)	$	(53,575	)	$	106,548


Cash and cash equivalents at the beginning of year	$	229,950		$	60,810		$	7,235
Cash and cash equivalents at the end of year	$	60,810		$	7,235		$	113,783
Supplemental schedule of non-cash investing and financing activities
Investment in subsidiaries and VIE directly financed by SINA	$	17,582		$	18,277		$	—

Operations and reorganization - Narrative Information (Details) $ in Millions			1 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($)	Apr. 17, 2014 shares	Apr. 30, 2014 USD ($) shares	Dec. 31, 2017 Vote	Jun. 29, 2015 Partnership
Class A ordinary shares
Operations and reorganization
Shares issued from conversion of preferred shares (in shares)			30,046,154
Number of votes each share is entitled to \| Vote				1
Number of Class A shares converted from Class B shares				1
Class A ordinary shares \| Alibaba
Operations and reorganization
Number of ordinary shares acquired by investor (in shares)		29,990,778
Class B ordinary shares
Operations and reorganization
Number of votes each share is entitled to \| Vote				3
IPO \| Class A ordinary shares
Operations and reorganization
Issuance of shares (in shares)			19,320,000
Proceeds from IPO \| $			$ 306.5
Weimeng
Operations and reorganization
Percentage of Direct/Indirect Economic Interest in VIEs				100.00%
Weibo Interactive
Operations and reorganization
Percentage of Direct/Indirect Economic Interest in VIEs				100.00%
Weibo HK
Operations and reorganization
Percentage of Direct/Indirect Economic Interest				100.00%
Weibo Technology
Operations and reorganization
Percentage of Direct/Indirect Economic Interest				100.00%
SINA
Operations and reorganization
Number of limited liability partnerships \| Partnership					2
SINA \| Weibo Funds, one
Operations and reorganization
Equity interest percentage owned by parent					55.00%
SINA \| Weibo Funds, two
Operations and reorganization
Equity interest percentage owned by parent					85.00%
SINA \| Transfer of Equity Interest in Weibo Interactive
Operations and reorganization
Consideration for transfer of equity interest to group \| $	$ 22.0

Operations and reorganization - Assets, Liabilities, Statement of Operations and Cash Flows (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operations and reorganization
Allocated expenses from SINA	$ 41,136,000	$ 25,703,000	$ 24,678,000
Interest-free loans to the VIE's shareholders	86,900,000	9,400,000
Aggregate accumulated losses	33,300,000	54,500,000
Assets and liabilities of the VIEs and their subsidiaries
Cash, cash equivalents and short-term Investments	1,792,683,000	395,954,000
Property and equipment, net	33,793,000	22,816,000
Intangible assets	517,000	1,100,000
Goodwill	13,420,000	10,266,000	11,117,000
Long-term investments	452,337,000	399,933,000	294,679,000	$ 63,777,000
Accounts payable	134,950,000	48,997,000
Accrued and other liabilities	268,615,000	180,142,000
Deferred revenues	81,311,000	48,964,000
Deferred tax liability	1,880,000	817,000
Results of operations of the VIEs and their subsidiaries
Net revenues	1,150,054,000	655,800,000	477,891,000
Net income (loss)	352,590,000	108,027,000	34,745,000
Cash flows of the VIE and its subsidiary
Net cash provided by (used in) operating activities	539,151,000	236,244,000	181,971,000
Net cash used in investing activities	(815,422,000)	(96,745,000)	(228,310,000)
Net cash provided by (used in) financing activities	883,578,000	3,035,000	4,959,000
Assets, except for registered capital of VIEs, that can only be used to settle obligations of the respective VIEs	0	0
Registered capital and non-distributable reserve funds of VIE and its subsidiaries	$ 137,300,000	56,200,000
Term of loan agreements	10 years
Service fees revenue charged to VIE	$ 618,100,000	335,600,000	232,400,000
Term of trademark license agreements	1 year
SINA
Operations and reorganization
Allocated expenses from SINA	$ 41,136,000	25,703,000	24,678,000
Assets and liabilities of the VIEs and their subsidiaries
Amount due from SINA	16,356,000	18,565,000
Consolidated VIEs
Operations and reorganization
Allocated expenses from SINA	21,400,000	12,300,000	8,400,000
Assets and liabilities of the VIEs and their subsidiaries
Cash, cash equivalents and short-term Investments	40,458,000	57,505,000
Accounts receivable	166,212,000	115,338,000
Property and equipment, net	146,000	357,000
Intangible assets	517,000	1,100,000
Goodwill	13,123,000	9,969,000
Prepayment for long-term investments	4,967,000	144,000
Long-term investments	74,935,000	49,195,000
Deferred tax assets	4,772,000	2,312,000
Amount due from SINA	4,677,000	12,163,000
Others	28,850,000	28,247,000
Total assets	338,657,000	276,330,000
Accounts payable	32,444,000	25,850,000
Accrued and other liabilities	114,239,000	64,879,000
Deferred revenues	54,651,000	38,313,000
Income tax payable	16,268,000	8,214,000
Amount due to the subsidiaries of the Group	57,639,000	171,460,000
Deferred tax liability	129,000	274,000
Total liabilities	275,370,000	308,990,000
Results of operations of the VIEs and their subsidiaries
Net revenues	906,129,000	530,598,000	391,568,000
Net income (loss)	21,252,000	(21,758,000)	(10,572,000)
Cash flows of the VIE and its subsidiary
Net cash provided by (used in) operating activities	(66,972,000)	(42,556,000)	158,290,000
Net cash used in investing activities	(34,720,000)	(28,577,000)	(39,965,000)
Net cash provided by (used in) financing activities	76,232,000	(1,148,000)
Net increase (decrease) in cash and cash equivalents	(25,460,000)	(72,281,000)	118,325,000
Cost of revenues
Operations and reorganization
Allocated expenses from SINA	13,699,000	11,022,000	6,550,000
Sales and marketing
Operations and reorganization
Allocated expenses from SINA	9,732,000	1,271,000	1,263,000
Product development
Operations and reorganization
Allocated expenses from SINA	11,312,000	9,094,000	12,981,000
General and administrative
Operations and reorganization
Allocated expenses from SINA	$ 6,393,000	$ 4,316,000	$ 3,884,000

Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cost of revenues
VAT and surcharges (as a percent)	6.70%
Sales and Marketing Expenses
Advertising and promotional expenses	$ 200,600	$ 92,200	$ 81,200
Operating leases
Allocated rental expenses from SINA	41,136	25,703	24,678
Long-term investments
Impairment charge	4,747	31,586	6,608
Impairment charge to AFS securities	$ 0	4,800	0
Stock options
Stock-based compensation
Vesting period	4 years
Service-Based Restricted share Units
Stock-based compensation
Vesting period	4 years
Rental expense
Operating leases
Allocated rental expenses from SINA	$ 4,500	3,900	3,500
Minimum
Operating leases
Lease period	6 months
Maximum
Operating leases
Lease period	5 years 6 months
Advertising and marketing revenues
Cost of revenues
Cultural business construction fees (as a percent)	3.00%
Taxes on advertising and marketing revenues	$ 90,600	$ 49,900	$ 35,300
Advertising and marketing revenues \| Maximum
Revenue recognition
Period over social display ad arrangements allow customers to place advertisements on particular areas of the Group's platform in particular formats	3 months
Value-added services revenues
Game-related service
Maximum period for recognition of revenues after purchase of in-game credits	1 month
Data licensing arrangement term	1 year

Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Depreciation expenses	$ 14.7	$ 13.3	$ 19.5
Computers and equipment \| Minimum
Property and equipment
Estimated useful lives of assets	3 years
Computers and equipment \| Maximum
Property and equipment
Estimated useful lives of assets	4 years
Furniture and fixtures
Property and equipment
Estimated useful lives of assets	5 years

Significant Accounting Policies - Intangible Assets Other Than Goodwill, Foreign Currency and Segment Reporting (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Foreign currency
Currency translation adjustments \| $	$ 37,822	$ (18,898)	$ (7,874)
Segment reporting
Number of principal business segments \| segment	2
Minimum
Intangible assets other than goodwill
Estimated useful lives of intangible assets	2 years
Maximum
Intangible assets other than goodwill
Estimated useful lives of intangible assets	5 years

Significant Accounting Policies - Concentration of Risks (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) customer Agency	Dec. 31, 2016 USD ($) customer Agency	Dec. 31, 2015 Agency
Concentration of risks
Cash, cash equivalents and short-term investments	$ 1,792,683	$ 395,954
Current liabilities denominated in RMB	484,876	278,103
Cash, cash equivalents and short-term investments \| Concentration of credit risk \| China
Concentration of risks
Cash, cash equivalents and short-term investments	$ 1,790,000	393,600
Maximum term of original maturity of time deposits	12 months
Cash, cash equivalents and short-term investments \| Concentration of foreign currency risks \| RMB
Concentration of risks
Cash, cash equivalents and short-term investments	$ 871,200	$ 335,700
Percentage of benchmark derived from specified source	49.00%	85.00%
Consolidated net revenues benchmark \| Customer concentration risk \| Alibaba
Concentration of risks
Percentage of benchmark derived from specified source	7.00%	9.00%	30.00%
Consolidated net accounts receivables benchmark \| Concentration of credit risk \| Alibaba
Concentration of risks
Percentage of benchmark derived from specified source	25.00%	21.00%
Consolidated net accounts receivables benchmark \| Concentration of credit risk \| Customer
Concentration of risks
Percentage of benchmark derived from specified source	10.00%	15.00%
Number of customers \| customer	1	1
Consolidated net accounts receivables benchmark \| Concentration of foreign currency risks \| RMB
Concentration of risks
Accounts receivable denominated in RMB	$ 170,100	$ 115,300
Current liabilities \| Concentration of foreign currency risks \| RMB
Concentration of risks
Current liabilities denominated in RMB	$ 475,600	$ 267,800
Percentage of benchmark derived from specified source	98.00%	96.00%
Advertising & Marketing \| Consolidated net revenues benchmark \| Customer concentration risk \| Top 10 advertising agencies \| China
Concentration of risks
Number of advertising agencies \| Agency	10	10	10
Percentage of benchmark derived from specified source	23.00%	22.00%	15.00%

Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash and cash equivalents:
Cash	$ 1,000,953	$ 364,766	$ 237,440	$ 284,865
Short-term investments:
Bank time deposits	791,730	31,188
Total cash, cash equivalents and short-term investments	1,792,683	395,954
Interest income	$ 17,900	$ 7,600	$ 5,500

Long-term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Long-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Long-term investments
Balance at the beginning of the year	$ 399,933	$ 294,679	$ 63,777
Investments made	54,083	152,091	252,256
Income (loss) from equity method investments	1,030	(130)	(6)
Disposal of investments		(11,010)	(13,134)
Dividend received from equity method investment	(267)
Impairment on investments	(4,747)	(31,586)	(6,608)
Unrealized loss	(995)	(2,557)	(198)
Currency translation adjustment	3,300	(1,554)	(1,408)
Balance at the end of year	452,337	399,933	294,679	$ 63,777
Investment related impairment	4,747	40,161	8,005
Cost Method
Long-term investments
Balance at the beginning of the year	390,330	281,707	50,594
Investments made	31,776	147,767	252,256
Disposal of investments		(6,010)	(13,134)
Impairment on investments	(4,747)	(31,586)	(6,608)
Currency translation adjustment	2,997	(1,548)	(1,401)
Balance at the end of year	420,356	390,330	281,707	50,594
Equity Method
Long-term investments
Balance at the beginning of the year	4,329	141	154
Investments made	22,307	4,324
Income (loss) from equity method investments	1,030	(130)	(6)
Dividend received from equity method investment	(267)
Currency translation adjustment	303	(6)	(7)
Balance at the end of year	27,702	4,329	141	154
Available-for-Sale Securities
Long-term investments
Balance at the beginning of the year	5,274	12,831	13,029
Investments made				15,100
Disposal of investments		(5,000)
Unrealized loss	(995)	(2,557)	(198)
Balance at the end of year	$ 4,279	5,274	$ 12,831	$ 13,029
Impairment charged to net income		4,800
Online-to-offline business
Long-term investments
Impairment on investments		(19,000)
Employment-oriented social company
Long-term investments
Impairment on investments		$ (10,500)

Acquisitions - Weibo funds (Details) $ in Millions		12 Months Ended
Acquisitions - Weibo funds (Details) $ in Millions	Jun. 30, 2015 USD ($) fund	Dec. 31, 2017 item	Dec. 31, 2016 item
Acquisitions
Number of immaterial acquisitions		1
Number of new acquisitions			0
Transfer of Equity Interest in Weibo Funds \| SINA
Acquisitions
Number of funds acquired \| fund	2
Consideration for transfer of equity interest \| $	$ 22.0
Transfer of Equity Interest in Weibo Funds \| SINA \| Weibo Funds, one
Acquisitions
Percentage of equity interest transferred to Group	55.00%
Transfer of Equity Interest in Weibo Funds \| SINA \| Weibo Funds, two
Acquisitions
Percentage of equity interest transferred to Group	85.00%

Acquisitions - Changes in the Group's Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in the Group's goodwill by segment
Balance at the beginning of the year	$ 10,266,000	$ 11,117,000
New acquisition	2,318,000
Currency translation adjustment	836,000	(851,000)
Balance at the end of the year	13,420,000	10,266,000	$ 11,117,000
Impairment of goodwill	0	0	0
Other
Changes in the Group's goodwill by segment
Balance at the beginning of the year	10,266,000	11,117,000
New acquisition	2,318,000
Currency translation adjustment	836,000	(851,000)
Balance at the end of the year	$ 13,420,000	$ 10,266,000	$ 11,117,000

Acquisitions - Future Amortization Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Intangible assets, net	$ 517	$ 1,100
Amortization expense	600	$ 700	$ 1,500
Future estimated amortization expenses
2018	517
2019 and thereafter	0
Total expected amortization expense	$ 517

Stock-Based Compensation - Incentive Plan Details (Details) - shares		1 Months Ended		12 Months Ended
	Jan. 01, 2015	Mar. 31, 2014	Aug. 31, 2010	Dec. 31, 2015
Stock-Based Compensation
Number of additional shares for the plan				21,684,000
2010 Plan
Stock-Based Compensation
Term of share incentive plan			10 years
Ordinary shares reserved for issuance			35,000,000
Amount that maximum number of ordinary shares available for issuance is reduced for every share issued pursuant to share option or share appreciation right			1
Amount that maximum number of ordinary shares available for issuance is reduced for every share issued as restricted shares or pursuant to restricted share units			1.75
2014 Plan
Stock-Based Compensation
Term of share incentive plan	10 years
Ordinary shares reserved for issuance		4,600,000
Number of additional shares for the plan		1,000,000
One-time percentage increase on January 1, 2015 for maximum aggregate number of shares which may be issued (as a percent)	10.00%

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock-based compensation
Stock-based compensation expense	$ 48,037	$ 36,902	$ 26,399
Amortization period	4 years
Cost of revenues
Stock-based compensation
Stock-based compensation expense	$ 3,716	2,616	1,196
Sales and marketing
Stock-based compensation
Stock-based compensation expense	8,264	5,357	3,209
Product development
Stock-based compensation
Stock-based compensation expense	21,879	15,076	10,210
General and administrative
Stock-based compensation
Stock-based compensation expense	$ 14,178	$ 13,853	$ 11,784

Stock-Based Compensation - Number of Shares Available for Issuance (Details) - USD ($)	1 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of shares available for issuance
Outstanding number of shares available for issuance at the beginning of the year (in shares)		18,878,000	20,217,000	2,738,000
Addition (in shares)				21,684,000
Granted (in shares)		(736,000)	(1,917,000)	(4,851,000)
Cancelled/expired/forfeited (in shares)		398,000	578,000	646,000
Outstanding number of shares available for issuance at the end of the year (in shares)		18,540,000	18,878,000	20,217,000	2,738,000
Aggregate Intrinsic Value
Fair value per ordinary share (in dollars per share)		$ 103.46	$ 40.60	$ 19.50
Proceeds from employee options exercised		$ 2,285,000	$ 4,183,000	$ 7,822,000
2014 Plan
Number of shares available for issuance
Addition (in shares)	1,000,000
Stock options
Options Outstanding
Outstanding at the beginning of the year (in shares)		2,587,000	6,303,000	14,330,000
Exercised (in shares)		(2,122,000)	(3,625,000)	(7,309,000)
Cancelled/expired/forfeited (in shares)		(28,000)	(91,000)	(718,000)
Outstanding at the end of the year (in shares)		437,000	2,587,000	6,303,000	14,330,000
Vested and expected to vest at the end of the year (in shares)		437,000	2,572,000
Exercisable at the end of the year (in shares)		437,000	2,433,000
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per share)		$ 1.41	$ 1.26	$ 1.28
Exercised (in dollars per share)		1.04	1.10	1.11
Cancelled/expired/forfeited (in dollars per share)		0.68	3.37	3.22
Outstanding at the end of the year (in dollars per share)		3.24	1.41	$ 1.26	$ 1.28
Vested and expected to vest at the end of the year (in dollars per share)		3.24	1.40
Exercisable at the end of the year (in dollars per share)		$ 3.24	$ 1.28
Weighted Average Remaining Contractual Life (In years)
Outstanding at the end of the year		2 years	1 year 7 months 6 days	2 years 4 months 24 days	3 years 2 months 12 days
Vested and expected to vest at the end of the year		2 years	1 year 7 months 6 days
Exercisable at the end of the year		2 years	1 year 4 months 24 days
Aggregate Intrinsic Value
Outstanding at the end of the year		$ 43,800,000	$ 101,403,000	$ 114,975,000	$ 185,684,000
Vested and expected to vest at the end of the year		43,800,000	100,819,000
Exercisable at the end of the year		43,800,000	95,678,000
Total intrinsic value of options exercised		135,200,000	129,300,000	106,200,000
Proceeds from employee options exercised		2,300,000	4,200,000	$ 7,800,000
Unrecognized compensation cost		$ 0	$ 1,100,000
Stock options \| 2014 Plan
Options Outstanding
Granted (in shares)		0	0	0
Restricted share units \| 2014 Plan
Number of shares available for issuance
Restricted shares units granted (in shares)		700,000	1,900,000	4,900,000

Stock-Based Compensation - Summary of Option Activities (Details) - Stock options - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Range of Exercise Prices
Options Outstanding (in shares)	437	2,587
Weighted Average Exercise Price (in dollars per share)	$ 3.24	$ 1.41
Options Exercisable (in shares)	437	2,433
Weighted Average Exercise Price (in dollars per share)	$ 3.24	$ 1.28
Weighted Average Remaining Contractual Life (In years)	2 years	1 year 7 months 6 days
$0.36 - $0.41
Range of Exercise Prices
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)		$ 0.36
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)		$ 0.41
Options Outstanding (in shares)		1,639
Weighted Average Exercise Price (in dollars per share)		$ 0.36
Options Exercisable (in shares)		1,639
Weighted Average Exercise Price (in dollars per share)		$ 0.36
Weighted Average Remaining Contractual Life (In years)		8 months 12 days
$0.96 - $1.80
Range of Exercise Prices
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	$ 0.96	$ 0.96
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 1.80	$ 1.80
Options Outstanding (in shares)	31	79
Weighted Average Exercise Price (in dollars per share)	$ 0.97	$ 0.97
Options Exercisable (in shares)	31	79
Weighted Average Exercise Price (in dollars per share)	$ 0.97	$ 0.97
Weighted Average Remaining Contractual Life (In years)	2 months 12 days	1 year 2 months 12 days
$3.25 - $3.36
Range of Exercise Prices
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	$ 3.25	$ 3.25
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 3.36	$ 3.36
Options Outstanding (in shares)	179	341
Weighted Average Exercise Price (in dollars per share)	$ 3.33	$ 3.33
Options Exercisable (in shares)	179	338
Weighted Average Exercise Price (in dollars per share)	$ 3.33	$ 3.33
Weighted Average Remaining Contractual Life (In years)	1 year 4 months 24 days	2 years 6 months
$3.43 - $3.50
Range of Exercise Prices
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	$ 3.43	$ 3.43
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 3.50	$ 3.50
Options Outstanding (in shares)	227	528
Weighted Average Exercise Price (in dollars per share)	$ 3.48	$ 3.48
Options Exercisable (in shares)	227	377
Weighted Average Exercise Price (in dollars per share)	$ 3.48	$ 3.48
Weighted Average Remaining Contractual Life (In years)	2 years 7 months 6 days	3 years 8 months 12 days

Stock-Based Compensation - Restricted Share Units (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Performance-Based Restricted Share Units
Shares Granted
Outstanding at the beginning of the year (in shares)	108,000
Awarded (in shares)	155,000	111,000	0
Vested (in shares)	(102,000)
Cancelled (in shares)	(32,000)	(3,000)
Outstanding at the end of the year (in shares)	129,000	108,000
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the year (in dollars per share)	$ 27.00
Awarded (in dollars per share)	50.45	$ 27.00
Vested (in dollars per share)	27.00
Cancelled (in dollars per share)	46.42	27.00
Outstanding at the end of the year (in dollars per share)	$ 50.32	$ 27.00
Unrecognized compensation cost	$ 0.7	$ 0.3
Service-Based Restricted share Units
Shares Granted
Outstanding at the beginning of the year (in shares)	5,458,000	6,501,000	3,507,000
Awarded (in shares)	581,000	1,806,000	4,851,000
Vested (in shares)	(2,406,000)	(2,274,000)	(1,211,000)
Cancelled (in shares)	(366,000)	(575,000)	(646,000)
Outstanding at the end of the year (in shares)	3,267,000	5,458,000	6,501,000
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the year (in dollars per share)	$ 17.23	$ 13.98	$ 16.44
Awarded (in dollars per share)	62.87	24.94	12.41
Vested (in dollars per share)	17.01	14.73	14.69
Cancelled (in dollars per share)	17.72	14.58	14.18
Outstanding at the end of the year (in dollars per share)	$ 25.45	$ 17.23	$ 13.98
Unrecognized compensation cost	$ 66.7
Expected weighted-average recognition period for unrecognized compensation cost	2 years 8 months 12 days
Total fair value vested	$ 40.9	$ 33.5	$ 17.8

Other Balance Sheet Components - Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, net:
Total gross amount	$ 178,214	$ 122,583
Allowance for doubtful accounts:
Balance at the beginning of the year	(6,529)	(1,375)	$ (2,440)
Reversal (additional provision) charged to expenses, net	(5,478)	(7,787)	368
Write-off	3,893	2,633	697
Balance at the end of the year	(8,114)	(6,529)	$ (1,375)
Accounts receivable, net	170,100	116,054
Alibaba
Accounts receivable, net:
Total gross amount	42,832	24,293
Allowance for doubtful accounts:
Balance at the beginning of the year	0
Balance at the end of the year	0	0
Accounts receivable, net	42,832	24,293
Other related parties
Accounts receivable, net:
Total gross amount	29,696	31,589
Allowance for doubtful accounts:
Balance at the beginning of the year	(1,483)
Balance at the end of the year	0	(1,483)
Accounts receivable, net	29,696	30,106
Third parties
Accounts receivable, net:
Total gross amount	105,686	66,701
Allowance for doubtful accounts:
Balance at the beginning of the year	(5,046)
Balance at the end of the year	(8,114)	(5,046)
Accounts receivable, net	$ 97,572	$ 61,655

Other Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Prepaid expenses and other current assets:
Rental and other deposits	$ 2,233	$ 3,965
Prepayment for investments	20,881	24,953
Advertising prepayment	3,959	5,267
Prepayment to outsourced service providers	5,369	4,043
Amounts deposited by users	25,277	21,203
Content fees	7,393	2,111
Others	4,121	5,122
Prepaid expenses and other current assets	$ 69,233	$ 66,664

Other Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property and equipment, net:
Property and equipment, gross	$ 121,694	$ 98,801
Less: Accumulated depreciation	(87,901)	(75,985)
Property and equipment, net	33,793	22,816
Computers and equipment
Property and equipment, net:
Property and equipment, gross	113,558	94,170
Leasehold improvements
Property and equipment, net:
Property and equipment, gross	4,321	2,054
Furniture and fixtures
Property and equipment, net:
Property and equipment, gross	1,241	922
Others
Property and equipment, net:
Property and equipment, gross	$ 2,574	$ 1,655

Other Balance Sheet Components - Accrued and other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued and other liabilities:
Payroll and welfare	$ 57,848	$ 33,786
Marketing expenses	53,380	40,968
Payroll withholding taxes	3,547	3,547
Sales rebates	60,663	31,598
Professional fees	6,170	4,255
VAT and other tax payable	51,563	35,728
Payable to other service providers	362	1,457
Amounts due to users	25,277	21,203
Others	9,805	7,600
Total accrued and other liabilities	$ 268,615	$ 180,142

Income Taxes (Details) $ / shares in Units, $ in Thousands		12 Months Ended
Income Taxes (Details) $ / shares in Units, $ in Thousands	Feb. 22, 2008	Dec. 31, 2017 USD ($) jurisdiction $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Income taxes
Number of taxable jurisdictions \| jurisdiction		2
Components of income before income taxes
Income before income tax expenses		$ 417,111	$ 109,980	$ 36,780
Loss from non-China operations		(52,261)	(60,193)	(28,016)
Income from China operations		469,372	170,173	64,796
Income tax expense applicable to China operations		$ 66,746	$ 4,316	$ 2,591
Effective tax rate for China operations (as a percent)		14.20%	2.50%	4.00%
Loss from investment impairments		$ (4,747)	$ (31,586)	$ (6,608)
Income tax rate (as a percent)		25.00%	25.00%	25.00%
Composition of income tax expenses for China operations
Deferred tax benefits		$ (1,503)	$ (4,630)	$ (977)
Current income tax expenses		68,249	8,946	3,568
Income tax expenses		$ 66,746	$ 4,316	$ 2,591
Reconciliation of the statutory tax rate to the effective tax rate for China operations
Statutory EIT rate (as a percent)		25.00%	25.00%	25.00%
Effect on tax holiday and preferential tax treatment (as a percent)		(11.60%)	(29.60%)	(24.20%)
Permanent differences (as a percent)		0.20%	1.20%	0.50%
Change in valuation allowance (as a percent)		0.60%	5.90%	2.70%
Effective tax rate for China operations (as a percent)		14.20%	2.50%	4.00%
Deferred tax assets:
Net operating loss carry forwards		$ 10,280	$ 32,158
Less: valuation allowance		(10,280)	(32,158)
Depreciation, accounts receivable, accrued and other liabilities		19,931	13,957
Less: valuation allowance		(11,629)	(8,576)
Net deferred tax assets (included in other assets)		8,302	5,381
Deferred tax liabilities:
Acquired intangible assets		129	274
Depreciation		527	362
Others		1,224	181
Total deferred tax liabilities		1,880	817
Valuation allowance on deferred tax assets		$ 21,900	40,700
Historical rate for valuing deferred tax assets (as a percent)		25.00%
Cumulative loss		$ 152,949	(199,641)
Net operating loss carryforwards expired amount		96,200
SINA
Components of income before income taxes
Net operating loss carry forwards		18,600
Deferred tax liabilities:
Cumulative loss		(22,500)
Weibo Technology
Reconciliation of the statutory tax rate to the effective tax rate for China operations
Effect of tax exemption			$ 50,400	$ 15,700
Effect of preferential tax treatment		$ 52,600
Effect of tax exemption and preferential tax on basic net income per share (USD per share) \| $ / shares		$ 0.25	$ 0.23	$ 0.08
Non-China
Components of income before income taxes
Loss from investment impairments			$ 23,800
Cayman Islands
Components of income before income taxes
Withholding income tax on dividends distributed by subsidiaries to its immediate holding entity outside China (as a percent)		0.00%
Hong Kong
Components of income before income taxes
Income tax rate (as a percent)		16.50%	16.50%	16.50%
Net operating loss carry forwards		$ 2,500
Reconciliation of the statutory tax rate to the effective tax rate for China operations
Statutory EIT rate (as a percent)		16.50%	16.50%	16.50%
China
Components of income before income taxes
Withholding income tax on dividends distributed by subsidiaries to its immediate holding entity outside China (as a percent)		10.00%
Income tax rate (as a percent)		25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%
Net operating loss carry forwards		$ 41,100	$ 129,300
Maximum percentage of withholding income tax on dividends distributed by subsidiaries to its immediate holding entity in Hong Kong		5.00%
Percentage of ownership interests held by foreign investors		25.00%
Percentage of withholding income tax on dividends distributed by PRC subsidiaries to its immediate holding company in Hong Kong		5.00%
Reconciliation of the statutory tax rate to the effective tax rate for China operations
Statutory EIT rate (as a percent)		25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%
China \| Software enterprise
Components of income before income taxes
Period of income tax exemption	2 years
Reduction in preferential tax rate (as a percent)	50.00%
Preferential statutory rate (as a percent)	12.50%	12.50%
Period of reduced preferential income tax rate	3 years

Related Party Transactions (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related party transactions
Costs and expenses allocated from SINA		$ 41,136	$ 25,703	$ 24,678
SINA
Related party transactions
Principal and interest expense of loan from SINA		60,000		2,863
Principal and interest income of loan to SINA's subsidiary		62,000
Revenue billed through SINA		64,093	39,285	22,114
Costs and expenses allocated from SINA		41,136	25,703	24,678
Other costs and expenses billed by SINA		22,900	20,300	29,400
Related party outstanding balance:
Accounts receivable due from related parties		16,356	18,565
SINA \| U.S. dollar-denominated Matching Loan from SINA
Related party transactions
Loan agreement term	1 year
Principal and interest expense of loan from SINA		61,500
Interest expense on matching loan from SINA		1,537
SINA \| RMB-denominated Matching Loan to SINA's Subsidiary
Related party transactions
Loan agreement term	1 year
Principal and interest income of loan to SINA's subsidiary		64,000
Interest income on matching loan to SINA		1,735
SINA \| Short-term Loan
Related party transactions
Amount of loan		2,000
Alibaba
Related party transactions
Advertising and marketing revenues from related party		84,688	57,908	143,650
Services provided by Alibaba		32,734	13,988	4,515
Related party outstanding balance:
Accounts receivable due from related parties		42,832	24,293
Alibaba \| Strategic cooperation with Alibaba
Related party transactions
Advertising and marketing revenues from related party				137,400
Other related parties
Related party transactions
Advertising and marketing revenues from related party		71,600	45,600	29,200
Value-added services revenues		21,400	600	2,100
Amount of promotional services from related parties		4,100	10,600	$ 7,800
Related party outstanding balance:
Due from related parties		29,700	30,100
Accrued and other liabilities due to other related parties		$ 5,000	$ 9,300

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
China Contribution Plan
Employee Benefit Plans
Employer contribution under China Contribution Plan	$ 38.0	$ 31.4	$ 29.7

Net Income per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income attributable to Weibo	$ 352,590	$ 108,027	$ 34,745
Denominator:
Weighted average ordinary shares outstanding (in shares)	220,555,000	214,745,000	208,163,000
Basic net income per share attributable to Weibo (in dollars per share)	$ 1.60	$ 0.50	$ 0.17
Numerator:
Net income attributable for calculating diluted net income per share	$ 352,590	$ 108,027	$ 34,745
Denominator:
Weighted average ordinary shares outstanding (in shares)	220,555,000	214,745,000	208,163,000
Weighted average ordinary shares equivalents:
Effects of dilutive securities (in shares)	4,800,000	8,100,000	9,800,000
Shares used in computing diluted net income per share attributable to Weibo (in shares)	225,363,000	222,859,000	217,918,000
Diluted net income per share attributable to Weibo (in dollars per share)	$ 1.56	$ 0.48	$ 0.16
Stock options
Anti-dilutive share
Anti-dilutive share excluded from the calculation of diluted net income per share	0	30,000	400,000
Weighted average ordinary shares equivalents:
Effects of dilutive securities (in shares)	1,213,000	4,334,000	8,572,000
Restricted share units
Anti-dilutive share
Anti-dilutive share excluded from the calculation of diluted net income per share	0	30,000	400,000
Weighted average ordinary shares equivalents:
Effects of dilutive securities (in shares)	3,595,000	3,780,000	1,183,000
2022 Notes
Anti-dilutive share
Anti-dilutive share excluded from the calculation of diluted net income per share	1,200,000

Segment Information (Details) $ in Thousands	12 Months Ended
Segment Information (Details) $ in Thousands	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Summary information by segment
Number of principal business segments \| segment	2
Revenues	$ 1,150,054	$ 655,800	$ 477,891
Advertising & Marketing
Summary information by segment
Revenues	996,745	570,982	402,415
Value-added services
Summary information by segment
Revenues	$ 153,309	$ 84,818	$ 75,476

Profit Appropriation and Restricted Net Assets (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) fund	Dec. 31, 2016 USD ($)
Profit Appropriation and Restricted Net Assets
Minimum percentage of after-tax profit transferred by Chinese subsidiaries to general reserve fund	10.00%
Maximum percentage criteria for appropriation of after-tax profit of Chinese subsidiaries to general reserve fund	50.00%
Number of reserve funds except general reserve fund, appropriation at the entity's discretion \| fund	2
Minimum percentage of after-tax profit transferred by VIEs to statutory reserve fund	10.00%
Maximum percentage criteria for in appropriation of after-tax profit by VIEs to certain statutory reserve funds	50.00%
Reserves made to non-distributable reserve fund (in dollars)	$ 73.6	$ 28.0
Net assets subject to restriction for the Group (in dollars)	$ 334.8
Percent of restricted net assets of total consolidated net assets	28.10%

Financial Instruments - Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value of Financial Instruments
Bank time deposits	$ 791,730	$ 31,188
Financial instruments measured on a recurring basis
Fair Value of Financial Instruments
Bank time deposits	791,730	31,188
Available-for-sale securities	4,279	5,274
Total	796,009	36,462
Financial instruments measured on a recurring basis \| Quoted Prices in Active Market for Identical Assets (Level 1)
Fair Value of Financial Instruments
Available-for-sale securities	4,279	5,274
Total	4,279	5,274
Financial instruments measured on a recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value of Financial Instruments
Bank time deposits	791,730	31,188
Total	$ 791,730	$ 31,188

Financial Instruments - Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Key inputs used in investor option liability valuation
Impairment loss for available-for-sale investments	$ 0.0	$ 4.8	$ 0.0
Financial instruments measured on a recurring basis
Key inputs used in investor option liability valuation
Impairment loss for available-for-sale investments	$ 0.0	$ 4.8	$ 0.0

Financial Instruments - Non-recurring Basis (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the fair value measurements using significant unobservable inputs
Investment related impairment	$ 4,747,000	$ 40,161,000	$ 8,005,000
Write-down of goodwill	$ 0	0	0
Significant Unobservable Inputs (Level 3) \| Non-recurring \| Minimum
Reconciliation of the fair value measurements using significant unobservable inputs
Discount rate (as a percent)	20.00%
Significant Unobservable Inputs (Level 3) \| Non-recurring \| Maximum
Reconciliation of the fair value measurements using significant unobservable inputs
Discount rate (as a percent)	22.00%
Significant Unobservable Inputs (Level 3) \| Non-recurring \| Certain investments under cost method and equity method were measured using significant unobservable inputs
Reconciliation of the fair value measurements using significant unobservable inputs
Fair value of investments	$ 0	0
Investment related impairment	$ 4,700,000	$ 35,400,000	$ 8,000,000

Convertible Debt (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares
Convertible Debt
Proceeds from issuance of the Notes	$ 879,293
2022 Notes
Convertible Debt
Aggregate principal amount	$ 900,000
Coupon interest (as a percent)	1.25%
Initial conversion price (in dollars per ADS) \| $ / shares	$ 133.27
Proceeds from issuance of the Notes	$ 879,300
Issuance costs	$ 20,700
Class A ordinary shares \| 2022 Notes
Convertible Debt
Conversion ratio	1

Commitments and Contingencies (Details)	3 Months Ended	12 Months Ended
Commitments and Contingencies (Details)	Aug. 31, 2017 action	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 26, 2018 defendant
Commitments and Contingencies
Lease expense		$ 9,200,000	$ 14,400,000	$ 15,500,000
Operating lease commitments
Total		34,005,000
Less than One Year		8,792,000
One to Three Years		17,011,000
Three to Five Years		8,202,000
Purchase commitments
Total		384,621,000
Less than One Year		366,939,000
One to Three Years		17,627,000
Three to Five Years		55,000
Notes 2022 commitments
Total		956,750,000
Less than One Year		13,219,000
One to Three Years		22,500,000
Three to Five Years		921,031,000
Two putative securities class actions
Contingency
Number of putative securities class actions filed in June and August 2017 \| action	2
Number of individual defendant filed a motion to dismiss the amended complaint \| defendant					1
Accrued contingencies		0
2022 Notes
Contingency
Aggregate principal amount		$ 900,000,000
Interest rate (as a percent)		1.25%

Additional Information-Condensed Financial Statements of Weibo Corporation - Balance Sheets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional Information
Minimum percentage of after-tax profit to reserve fund	10.00%
Current assets:
Cash and cash equivalents	$ 1,000,953	$ 364,766	$ 237,440	$ 284,865
Short-term investments	791,730	31,188
Prepaid expenses and other current assets	69,233	66,664
Total current assets	2,048,372	597,237
Amount due from SINA	16,356	18,565
Total assets	2,561,819	1,036,944
LIABILITIES AND SHAREHOLDERS' EQUITY
Accrued and other liabilities	268,615	180,142
Convertible debt	879,983
Long-term Liabilities	882,149	1,483
Total liabilities	1,367,025	279,586
Commitments and contingencies
Shareholders' equity:
Ordinary shares: $0.00025 par value; 2,400,000 and 2,400,000 shares (including 1,800,000 Class A ordinary shares, 200,000 Class B ordinary shares and 400,000 shares to be designated)authorized; 218,076 and 222,706 shares (including 120,927 Class A ordinary shares and 101,779 Class B ordinary shares) issued and outstanding as of December 31, 2016 and 2017, respectively.	56	55
Additional paid-in capital	1,030,048	979,805
Accumulated other comprehensive income (loss)	9,534	(26,994)
Retained earnings (Accumulated deficit)	152,949	(199,641)
Total Weibo shareholders' equity	1,192,587	753,225
Total liabilities and shareholders' equity	2,561,819	1,036,944
Weibo Corporation
Current assets:
Cash and cash equivalents	113,783	7,235	$ 60,810	$ 229,950
Short-term investments	782,530	30,401
Prepaid expenses and other current assets	5,579	5,682
Total current assets	901,892	43,318
Long-term investments	376,579	349,502
Investment in subsidiaries, VIE and VIE's subsidiaries	808,150	367,114
Amount due from SINA		89
Total assets	2,086,621	760,023
LIABILITIES AND SHAREHOLDERS' EQUITY
Accrued and other liabilities	13,765	6,132
Convertible debt	879,983
Long-term Liabilities	286	666
Total liabilities	894,034	6,798
Commitments and contingencies
Shareholders' equity:
Ordinary shares: $0.00025 par value; 2,400,000 and 2,400,000 shares (including 1,800,000 Class A ordinary shares, 200,000 Class B ordinary shares and 400,000 shares to be designated)authorized; 218,076 and 222,706 shares (including 120,927 Class A ordinary shares and 101,779 Class B ordinary shares) issued and outstanding as of December 31, 2016 and 2017, respectively.	56	55
Additional paid-in capital	1,030,048	979,805
Accumulated other comprehensive income (loss)	9,534	(26,994)
Retained earnings (Accumulated deficit)	152,949	(199,641)
Total Weibo shareholders' equity	1,192,587	753,225
Total liabilities and shareholders' equity	$ 2,086,621	$ 760,023

Additional Information-Condensed Financial Statements of Weibo Corporation - Balance Sheets - (Parenthetical) (Details) - $ / shares shares in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00025	$ 0.00025
Ordinary shares, shares authorized	2,400,000	2,400,000
Ordinary shares, shares issued	222,706	218,076
Ordinary shares, shares outstanding	222,706	218,076
Class A ordinary shares
Balance sheets
Ordinary shares, shares authorized	1,800,000	1,800,000
Ordinary shares, shares issued	120,927
Ordinary shares, shares outstanding	120,927
Class B ordinary shares
Balance sheets
Ordinary shares, shares authorized	200,000	200,000
Ordinary shares, shares issued	101,779
Ordinary shares, shares outstanding	101,779
Ordinary shares to be designated
Balance sheets
Ordinary shares, shares authorized	400,000	400,000
Weibo Corporation
Balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00025	$ 0.00025
Ordinary shares, shares authorized	2,400,000	2,400,000
Ordinary shares, shares issued	222,706	218,076
Ordinary shares, shares outstanding	222,706	218,076
Weibo Corporation \| Class A ordinary shares
Balance sheets
Ordinary shares, shares authorized	1,800,000	1,800,000
Ordinary shares, shares issued	120,927
Ordinary shares, shares outstanding	120,927
Weibo Corporation \| Class B ordinary shares
Balance sheets
Ordinary shares, shares authorized	200,000	200,000
Ordinary shares, shares issued	101,779
Ordinary shares, shares outstanding	101,779
Weibo Corporation \| Ordinary shares to be designated
Balance sheets
Ordinary shares, shares authorized	400,000	400,000

Additional Information-Condensed Financial Statements of Weibo Corporation - Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements of Comprehensive Income
Operating loss	$ 407,554	$ 140,980	$ 37,503
Interest and other income (expenses), net	13,260	8,757	6,344
Investment related impairment	(4,747)	(40,161)	(8,005)
Other income, net
Share of income of subsidiaries, VIE, and VIE's subsidiaries	1,030	(130)	(6)
Net income attributable to Weibo	352,590	108,027	34,745
Other comprehensive income (loss)
Currency translation adjustments (net of tax of nil, nil, and nil for 2015, 2016 and 2017, respectively)	37,822	(18,898)	(7,874)
Available-for-sale securities:
Change in unrealized loss from available-for-sale securities (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	(995)	(2,557)	(198)
Reclassification adjustment for net loss included in net income (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)		4,822
Net change, net of tax	(995)	2,265	(198)
Comprehensive income attributable to Weibo	389,118	91,668	26,946
Weibo Corporation
Statements of Comprehensive Income
Operating loss	(945)	(1,891)	(1,279)
Interest and other income (expenses), net	(1,941)	1,763	4,759
Investment related impairment		(23,822)
Other income, net
Share of income of subsidiaries, VIE, and VIE's subsidiaries	355,476	131,977	31,265
Net income attributable to Weibo	352,590	108,027	34,745
Other comprehensive income (loss)
Currency translation adjustments (net of tax of nil, nil, and nil for 2015, 2016 and 2017, respectively)	37,523	(18,624)	(7,601)
Available-for-sale securities:
Change in unrealized loss from available-for-sale securities (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)	(995)	(2,557)	(198)
Reclassification adjustment for net loss included in net income (net of tax of nil, nil, and nil for 2015, 2016, and 2017, respectively)		4,822
Net change, net of tax	(995)	2,265	(198)
Comprehensive income attributable to Weibo	$ 389,118	$ 91,668	$ 26,946

Additional Information-Condensed Financial Statements of Weibo Corporation - Statements of Comprehensive Income (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements of Comprehensive Income
Currency translation adjustments, tax	$ 0	$ 0	$ 0
Change in unrealized loss from available-for-sale securities, tax	0	0	0
Reclassification adjustment for net loss included in net income, tax	0	0	0
Weibo Corporation
Statements of Comprehensive Income
Currency translation adjustments, tax	0	0	0
Change in unrealized loss from available-for-sale securities, tax	0	0	0
Reclassification adjustment for net loss included in net income, tax	$ 0	$ 0	$ 0

Additional Information-Condensed Financial Statements of Weibo Corporation - Statements of Cash flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements of Cash flow
Net cash provided by operating activities	$ 539,151	$ 236,244	$ 181,971
Purchase of short-term investments	(1,439,558)	(314,363)	(149,374)
Maturity of short-term investments	696,245	373,805	216,615
Investments and prepayments on equity investments	(54,640)	(155,122)	(268,758)
Net cash used in investing activities	(815,422)	(96,745)	(228,310)
Proceeds from convertible notes, net of debt issuance costs	879,293
Proceeds from employee options exercised	2,285	4,183	7,822
Net cash provided by financing activities	883,578	3,035	4,959
Cash and cash equivalents at the beginning of the year	364,766	237,440	284,865
Cash and cash equivalents at the end of the year	1,000,953	364,766	237,440
Weibo Corporation
Statements of Cash flow
Net cash provided by operating activities	3,996	1,025	5,317
Purchase of short-term investments	(781,000)	(30,046)	(148,863)
Maturity of short-term investments	30,046	97,798	218,762
Investments and prepayments on equity investments	(28,072)	(120,000)	(247,200)
Investment in subsidiaries		(6,535)	(4,978)
Net cash used in investing activities	(779,026)	(58,783)	(182,279)
Proceeds from convertible notes, net of debt issuance costs	879,293
Proceeds from employee options exercised	2,285	4,183	7,822
Loan from SINA	60,000
Repayment of loan from SINA	(60,000)
Net cash provided by financing activities	881,578	4,183	7,822
Net increase (decrease) in cash and cash equivalents	106,548	(53,575)	(169,140)
Cash and cash equivalents at the beginning of the year	7,235	60,810	229,950
Cash and cash equivalents at the end of the year	$ 113,783	7,235	60,810
Supplemental schedule of non-cash investing and financing activities
Investment in subsidiaries and VIE directly financed by SINA		$ 18,277	$ 17,582