Weibo (WB) 20-F 28 Apr 15 2014 FY Annual report (foreign) Financial data

Document_and_Entity_Informatio

Document and Entity Information	12 Months Ended
	Dec. 31, 2014
Entity Registrant Name	WEIBO Corp
Entity Central Index Key	1595761
Document Type	20-F
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Class A ordinary shares
Entity Common Stock, Shares Outstanding	87,648,811
Class B ordinary shares
Entity Common Stock, Shares Outstanding	116,009,222

COMBINED_AND_CONSOLIDATED_BALA

COMBINED AND CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$283,462	$246,436
Short-term investments	166,414	252,342
Accounts receivable due	120,210	47,304
Prepaid expenses and other current assets	16,104	5,693
Total current assets	586,190	551,775
Property and equipment, net	30,874	35,702
Intangible assets, net	3,539	3,071
Goodwill	11,652	7,517
Long-term investments	45,199	5,500
Other assets	327	3,369
Total assets	677,781	606,934
Current liabilities (including amounts of the combined and consolidated VIE without recourse to the primary beneficiaries of $87,402 and $173,106 as of December 31, 2013 and 2014, respectively. (Note 1)):
Accounts payable	2,420	824
Accrued liabilities due to third parties and employees	81,692	52,907
Accrued liabilities due to related parties (Note 9)	5,786	3,507
Deferred revenues	20,957	15,031
Amount due to SINA	1,717	267,722
Investor option liability		29,504
Total current liabilities	112,572	369,495
Long-term liabilities
Deferred tax liabilities	873	768
Total long-term liabilities	873	768
Total liabilities	113,445	370,263
Commitments and contingencies (Note 15)
Mezzanine equity (Note 3)
Total mezzanine equity		479,612
Shareholders' equity (deficit):
Ordinary shares: $0.00025 par value; 600,000 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; 150,392 and 203,658 shares (including 87,649 Class A ordinary shares and 116,009 Class B ordinary shares) issued and outstanding as of December 31, 2013 and 2014, respectively.	51	37
Additional paid-in capital	904,402	31,352
Accumulated other comprehensive income (loss)	-2,943	521
Accumulated deficit	-338,229	-274,851
Total Weibo shareholders' equity (deficit)	563,281	-242,941
Non-controlling interests	1,055
Total shareholders' equity(deficit)	564,336	-242,941
Total liabilities, mezzanine equity and shareholders' equity	677,781	606,934
Convertible preferred shares
Mezzanine equity (Note 3)
Total mezzanine equity		479,612
Third parties
Current assets:
Accounts receivable due	36,976	24,175
SINA and other related parties
Current assets:
Accounts receivable due	18,509	1,830
Alibaba
Current assets:
Accounts receivable due	$64,725	$21,299

COMBINED_AND_CONSOLIDATED_BALA1

COMBINED AND CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Allowance for doubtful accounts	$2,440	$3,242
Current liabilities	112,572	369,495
Ordinary shares, par value (in dollars per share)	$0.00	$0.00
Ordinary shares, shares authorized	2,400,000,000	600,000,000
Ordinary shares, shares issued	203,658,000	150,392,000
Ordinary shares, shares outstanding	203,658,000	150,392,000
Convertible preferred shares
Convertible preferred shares, par value (in dollars per share)		$0.00
Convertible preferred shares, shares authorized		100,000,000
Convertible preferred shares, shares issued		30,046,000
Convertible preferred shares, shares outstanding		30,046,000
Convertible preferred shares, redemption value (in dollars per share)		$16.79
Class A ordinary shares
Ordinary shares, shares authorized	1,800,000,000
Ordinary shares, shares issued	87,649,000
Ordinary shares, shares outstanding	87,649,000
Class B ordinary shares
Ordinary shares, shares authorized	200,000,000
Ordinary shares, shares issued	116,009,000
Ordinary shares, shares outstanding	116,009,000
Ordinary shares to be designated
Ordinary shares, shares authorized	400,000,000
Consolidated VIEs without recourse to the primary beneficiaries
Current liabilities	173,106	87,402
SINA and other related parties
Allowance for doubtful accounts	139	228
Third parties
Allowance for doubtful accounts	$2,301	$3,014

COMBINED_AND_CONSOLIDATED_STAT

COMBINED AND CONSOLIDATED STATEMENTS OF LOSS AND COMPREHENSIVE LOSS (USD $)	12 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Advertising and marketing revenues
Third parties	$129,644,000	$96,976,000	$51,049,000
Total advertising and marketing revenues	264,782,000	148,426,000	51,049,000
Other revenues	69,390,000	39,887,000	14,880,000
Total revenues	334,172,000	188,313,000	65,929,000
Costs and Expenses
Cost of revenues (including cost of revenues from related party of $3,484, nil, and nil for the year ended December 31, 2012, 2013 and 2014, respectively)	83,599,000	59,891,000	46,429,000
Sales and marketing (including sales and marketing from related parties of $nil, $878 and $11,160 for the year ended December 31, 2012, 2013 and 2014, respectively)	120,314,000	63,069,000	40,380,000
Product development	125,832,000	100,740,000	71,186,000
General and administrative	25,719,000	22,517,000	5,778,000
Total costs and expenses	355,464,000	246,217,000	163,773,000
Loss from operations	-21,292,000	-57,904,000	-97,844,000
Loss from equity method investment		-1,236,000	-1,340,000
Remeasurement gain upon obtaining control (Note 5)		3,116,000
Interest and other income (expenses), net (including interest expense on amount due to SINA of $4,923, $6,709, and $2,838 for the year ended December 31, 2012, 2013 and 2014, respectively)	6,758,000	-2,884,000	-4,853,000
Change in fair value of investor option liability (Note 14)	-46,972,000	21,064,000
Loss before income tax expenses (benefits)	-61,506,000	-37,844,000	-104,037,000
Less: Income tax expenses (benefits)	1,128,000	271,000	-1,551,000
Net loss	-62,634,000	-38,115,000	-102,486,000
Less: Net income attributable to the non-controlling interests	744,000
Net loss attributable to Weibo	-63,378,000	-38,115,000	-102,486,000
Other comprehensive income (loss)
Currency translation adjustments	-1,401,000	-372,000	18,000
Unrealized loss on available-for-sale securities	-2,067,000
Total comprehensive loss	-66,102,000	-38,487,000	-102,468,000
Less: Comprehensive loss attributable to non-controlling interests	740,000
Comprehensive loss attributable to Weibo's ordinary shareholders	-66,842,000	-38,487,000	-102,468,000
Basic net loss per share attributable to Weibo's ordinary shareholders (in dollars per share)	($0.34)	($0.26)	($0.73)
Shares used in computing basic net loss per share attributable to Weibo's ordinary shareholders	186,878	146,820	140,831
Diluted net loss per share attributable to Weibo's ordinary shareholders (in dollars per share)	($0.34)	($0.26)	($0.73)
Shares used in computing diluted net loss per share attributable to Weibo's ordinary shareholders	186,878	146,820	140,831
Alibaba
Advertising and marketing revenues
Related party	107,587,000	49,135,000
Other related parties
Advertising and marketing revenues
Related party	$27,551,000	$2,315,000

COMBINED_AND_CONSOLIDATED_STAT1

COMBINED AND CONSOLIDATED STATEMENTS OF LOSS AND COMPREHENSIVE LOSS (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
COMBINED AND CONSOLIDATED STATEMENTS OF LOSS AND COMPREHENSIVE LOSS
Cost of revenues from related party	$0	$0	$3,484,000
Sales and marketing from related parties	11,160,000	878,000	0
Interest expense on amount due to SINA	$2,838,000	$6,709,000	$4,923,000

COMBINED_AND_CONSOLIDATED_STAT2

COMBINED AND CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (DEFICIT) (USD $)	Ordinary Shares	Ordinary Shares	Ordinary Shares	Ordinary Shares	Additional Paid-In Capital	Additional Paid-In Capital	Additional Paid-In Capital	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Non-controlling Interests	SINA	Alibaba	IPO	Total
In Thousands, except Share data, unless otherwise specified	SINA	Alibaba	IPO	USD ($)	SINA	Alibaba	IPO	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)
		USD ($)	USD ($)		USD ($)	USD ($)	USD ($)
Balance at Dec. 31, 2011				$35				$26,597	$993	($134,250)					($106,625)
Balance (in shares) at Dec. 31, 2011				140,000,000
Increase (Decrease) in Shareholders' Equity (Deficit)
Issuance of ordinary shares pursuant to stock plan				1				1,230							1,231
Issuance of ordinary shares pursuant to stock plan (in shares)				3,445,000
Repurchase of vested options								-7,883							-7,883
Non-cash stock-based compensation								1,837							1,837
Net income (loss)										-102,486					-102,486
Currency translation adjustments									18						18
Balance at Dec. 31, 2012				36				21,781	1,011	-236,736					-213,908
Balance (in shares) at Dec. 31, 2012				143,445,000
Increase (Decrease) in Shareholders' Equity (Deficit)
Issuance of ordinary shares pursuant to stock plan								1,258							1,258
Issuance of ordinary shares pursuant to stock plan (in shares)				3,449,000
Issuance of ordinary shares (either in IPO or to related party)		1				39,037							39,038
Issuance of ordinary shares (either in IPO or to related party) (in shares)		3,498,000
Repurchase of vested options								-37,959							-37,959
Non-cash stock-based compensation								4,105							4,105
Deemed contribution from SINA								13,092				13,092			13,092
Legal transfer of Weibo Interactive and recognition of amount due to SINA								-10,080				-10,080			-10,080
Net income (loss)										-38,115					-38,115
Currency translation adjustments								118	-490						-372
Balance at Dec. 31, 2013				37				31,352	521	-274,851					-242,941
Balance (in shares) at Dec. 31, 2013				150,392,000											150,392,000
Increase (Decrease) in Shareholders' Equity (Deficit)
Issuance of ordinary shares pursuant to stock plan				1				1,918							1,919
Issuance of ordinary shares pursuant to stock plan (in shares)				3,900,000
Issuance of ordinary shares (either in IPO or to related party)			5			42,224	301,273						42,224	301,278
Issuance of ordinary shares (either in IPO or to related party) (in shares)		2,923,000	19,320,000
Deemed contribution from related party					61,176	15,300						61,176	15,300
Repurchase of ordinary shares from SINA					-42,224							-42,224
Repurchase of ordinary shares from SINA (in shares)	-2,923,000
Conversion of preferred shares into ordinary shares				8				479,604							479,612
Conversion of preferred shares into ordinary shares (in shares)				30,046,000
Non-cash stock-based compensation								13,779							13,779
Purchase of subsidiaries' shares from non-controlling interests											315				315
Deemed contribution from SINA												61,176			61,176
Net income (loss)										-63,378	744				-62,634
Currency translation adjustments									-1,397		-4				-1,401
Unrealized loss on available-for-sale securities									-2,067						-2,067
Balance at Dec. 31, 2014				$51				$904,402	($2,943)	($338,229)	$1,055				$564,336
Balance (in shares) at Dec. 31, 2014				203,658,000											203,658,000

COMBINED_AND_CONSOLIDATED_STAT3

COMBINED AND CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	($62,634,000)	($38,115,000)	($102,486,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	23,060,000	21,529,000	16,386,000
Stock-based compensation	13,779,000	4,105,000	1,837,000
Provision (reversal) for allowance for doubtful accounts	-802,000	2,345,000	897,000
Deferred income taxes	866,000	271,000	-1,551,000
Loss from equity method investment		1,236,000	1,340,000
Remeasurement gain upon obtaining control		-3,116,000
Change in fair value of investor option liability	46,972,000	-21,064,000
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from third parties	-11,998,000	-26,930,000	-258,000
Prepaid expenses and other current assets	-12,737,000	-2,204,000	-3,094,000
Other assets	-23,000
Accrued liabilities due to third parties and employees	32,770,000	35,854,000	779,000
Deferred revenues	5,799,000	12,638,000	2,217,000
Net cash used in operating activities	-24,679,000	-9,369,000	-103,642,000
Cash flows from investing activities:
Purchases of short-term investments	-230,161,000	-250,000,000	-117,564,000
Maturities of short-term investments	321,208,000	117,564,000
Investment and prepayment in long-term investments	-45,611,000	-8,885,000
Purchases of property and equipment	-14,743,000	-12,044,000	-18,962,000
Cash paid for business acquisition, net of cash acquired	-9,648,000
Net cash provided by (used in) investing activities	21,045,000	-153,365,000	-136,526,000
Cash flows from financing activities:
Proceeds from IPO, net of commission	306,491,000
Payment of offering expenses	-5,213,000
Proceeds from employees options exercised	1,508,000	991,000
Proceeds from the issuance of preferred and ordinary shares (Note 3)		585,799,000
Payment for ordinary shares and repurchase of vested options	-6,873,000	-45,876,000	-4,335,000
Funding from SINA	15,824,000	26,644,000	233,703,000
Repayment of amount due to SINA	-269,042,000	-159,816,000
Other financing activities		-989,000
Net cash provided by financing activities	42,695,000	406,753,000	229,368,000
Effect of exchange rate changes on cash and cash equivalents	-2,035,000	-489,000	18,000
Net increase (decrease) in cash and cash equivalents	37,026,000	243,530,000	-10,782,000
Cash and cash equivalents at the beginning of the year	246,436,000	2,906,000	13,688,000
Cash and cash equivalents at the end of the year	283,462,000	246,436,000	2,906,000
Supplemental disclosure of cash flow information
Cash paid for interest	-7,580,000
Supplemental schedule of non-cash investing and financing activities
Deemed contribution from SINA (Note 9)	61,176,000	13,092,000
Conversion of preferred shares to ordinary shares	479,612,000
Legal transfer of Weibo Interactive and recognition of amount due to SINA		-10,080,000
SINA and other related parties
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from related parties	-16,589,000	24,507,000	-26,567,000
Alibaba
Changes in assets and liabilities, net of acquisition:
Accounts receivable due from related parties	-43,426,000	-21,299,000
Supplemental schedule of non-cash investing and financing activities
Deemed contribution from related party	15,300,000
Other related parties
Changes in assets and liabilities, net of acquisition:
Due to related parties	2,279,000	-5,835,000	1,935,000
SINA
Changes in assets and liabilities, net of acquisition:
Due to related parties	2,747,000
Interest on amount due to SINA	-4,742,000	6,709,000	4,923,000
Cash flows from financing activities:
Repayment of amount due to SINA	-276,614,000	-159,816,000
Supplemental schedule of non-cash investing and financing activities
Deemed contribution from SINA (Note 9)	61,176,000	13,092,000
Deemed contribution from related party	61,176,000
Legal transfer of Weibo Interactive and recognition of amount due to SINA		($10,080,000)

Operations_and_reorganization

Operations and reorganization	12 Months Ended
	Dec. 31, 2014
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 timely information 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 social influence. Weibo generates the majority of its revenues from advertising and marketing services as well as other services, including game-related services, VIP membership and data licensing.
	Incorporated in the Cayman Islands, Weibo Corporation is a majority-owned 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. The company received $306.5 million in net proceeds from the issuance of new shares upon the IPO. 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 (Note 3). 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
	Weibo business was founded by SINA, its parent, in 2009. Prior to the establishment of the Company, the operations of Weibo business was carried out by various subsidiaries and variable interest entities (“VIEs”) of SINA (the “Predecessor Operations”). After its establishment, the Company has 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 or the wholly foreign-owned enterprise (“the WFOE”), is a subsidiary of Weibo HK. The Company’s VIE and its 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 its subsidiary:
	Company	Date of		Place of		Percentage of
		Incorporation		Incorporation		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 its subsidiary**
	Beijing Weimeng Technology Co., Ltd (“Weimeng” or the VIE)	August 9, 2010		PRC		100	%
	Beijing Weibo Interactive Internet Technology Co., Ltd. (‘‘Weibo Interactive’’)	Acquired in May 2013 (Note 5)		PRC		100	%
	Transfer of assets and liabilities relating to the Weibo business to the Group. According to the Company’s Shareholder Agreement dated April 29, 2013, the Group shall be liable for a loan payable to SINA for assets and liabilities incurred by SINA for the development of the Weibo business. The interest on amount due to SINA is calculated based on actual spending incurred by SINA for the development of Weibo business at each period end. The combined and consolidated statements of loss and comprehensive loss reflected a charge for interest on the amount due to SINA, as well as on the amounts included as accrued liabilities due to SINA, at prevailing market interest rates by reference to the three-month time deposit rate of The People’s Bank of China, which ranged from 2.55% to 3.05%. The loans are repayable upon demand. There is no written loan agreement signed between SINA and Weibo. The interest expenses incurred was $4.9 million, $6.7 million and $2.8 million for the years ended December 31, 2012, 2013 and 2014, respectively.  On April 29, 2013, SINA waived the interest charged to the Group in the amount of $8.5 million. The total waived amounts were accounted for as deemed contribution from SINA. In accordance with the Shareholder Agreement, the amount due to SINA after the waiver was $250 million and further cash outlay after April 29, 2013 to support the development of the Weibo business would increase the amount due to SINA. As of December 31, 2013, the Group recorded amount due to SINA of $267.7 million, including an interest payable balance of $4.8 million, all of which was repaid after the IPO.  As of December 31, 2014, Weibo had a $1.7 million payment due to SINA, which is interest free and payable on demand.  Such balance represented the unpaid portion related to the allocated expenses from SINA.
	Transfer of Equity Interests in Weibo Interactive. Starting in 2011, SINA held a 55% equity interest in Weibo Interactive, an online-game platform company incorporated in China, and accounted for such interest using the equity method of accounting, as it had no control over the operations and assets of such interest. Weibo Interactive has been providing game platform maintenance services to Weibo since 2012. In May 2013, SINA gained control of Weibo Interactive through a step acquisition in which the remaining 45% equity interest was obtained for a consideration of $4.6 million. In connection with the Reorganization, SINA entered into an agreement to transfer 100% equity interest in Weibo Interactive to the Group for a consideration of $10.1 million effective in December 2013 (Note 5).
	The transfer of Weibo Interactive to the Group was accounted for as a business combination between entities under common control, with financial statements presented for prior periods retrospectively adjusted to reflect the transfer from the first day SINA took control in May 2013. The investment in Weibo Interactive prior to the step-up acquisition was also reflected in the Group’s combined and consolidated financial statements as if the investment was held by the Group since 2012, the earliest period presented.
	The amounts recognized in the Group’s combined and consolidated financial statements reflect the assets and liabilities of Weibo Interactive at SINA’s historical carrying value. The net equity of Weibo Interactive was reflected in the Group’s combined and consolidated financial statements at the historical carrying value within the equity section as a deemed contribution from SINA. The $10.1 million of consideration payable to SINA was recognized when the transfer became legally effective in December 2013, which resulted in a decrease in equity and a corresponding increase in amount due to SINA. The service fees paid to Weibo Interactive prior to the May 2013 step-up acquisition were disclosed as related party transactions under cost of revenues in the Group’s combined and consolidated statements of loss and comprehensive loss. The service fees paid to Weibo Interactive after the step-up acquisition were eliminated as inter-company transactions.
	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 grants 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 grants 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 in effect unless terminated by SINA in case of the Company’s breach as provided in the agreement.
	Basis of Presentation for the Reorganization. Since the Group and the Predecessor Operations are under common control, the accompanying combined and 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 combined and consolidated financial statements have been prepared as if the current corporate structure, including the transfer of Weibo Interactive in December 2013, had been in existence throughout the periods presented.
	Only those assets and liabilities that are specifically identifiable to Weibo business are included in the Group’s combined and consolidated balance sheets. Accounts receivable amounts directly related to Weibo but for which SINA will receive payments and remit payment to the Group are included in the accounts receivable due from SINA, and, if any uncollectible losses arise from the accounts receivable due from SINA, such losses will pass through to the Group. Liabilities directly related to Weibo but for which SINA will make payment and receive reimbursement from the Group are included in the accrued liabilities due to related parties. The Group was liable for a payable to SINA for assets and liabilities incurred by SINA for the development of the Weibo business and presented as amount due to SINA in the combined and consolidated balance sheets. Loan from SINA is presented under cash flow from financing activities in the combined and consolidated statements of cash flows, whereas cash payment for billings from SINA for costs and expenses allocated is presented under operating activities. The Group’s statements of loss and comprehensive loss 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. Income tax liability is calculated based on a separate return basis as if the Group had filed a separate tax return.
	Total allocated expenses from SINA were as follows:
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Cost of revenues	$	17,769		$	14,760		$	4
	Sales and marketing	2,506			6,074			17,417
	Product development	21,111			19,256			18,362
	General and administrative	2,574			4,215			6,581
		$	43,960		$	44,305		$	42,360
	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.
	Combination and Consolidation
	The combined and consolidated financial statements include the accounts of the Company, its wholly-owned subsidiaries and its VIE, of which the Company is the primary beneficiary, and Weibo Interactive, an investment from July 2011 to May 2013. The transfer of Weibo Interactive in December 2013 was accounted for as a business combination between entities under common control with financial statements presented for prior periods retrospectively adjusted to reflect the transfer on a consolidated basis from the first day SINA took control in May 2013, and the financial statements were presented on a combined basis from July 2011 to May 2013 to include the equity method investment in Weibo Interactive. 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 Weimeng, or 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 (loss) 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 of 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, 2013 and 2014, the total amount of interest-free loans to the VIE’s shareholders was $1.5 million and $10.5 million, respectively. As of December 31, 2013 and 2014, the aggregate accumulated loss of the VIE was $13.6 million and $18.0 million, respectively, which were included in the Group’s combined and consolidated financial statements.
	The following table sets forth the assets, liabilities, results of operations and cashflows of the VIE and its subsidiary taken as a whole, including the Predecessor Operations, which are included in the Group’s combined and consolidated balance sheets and statements of loss and comprehensive loss:
		As of December 31,
		2013			2014
		(In thousands)
	Cash, Cash Equivalents and Short-term Investments	$	9,200		$	9,271
	Accounts receivable	46,575			118,891
	Property and equipment, net	1,155			2,092
	Goodwill	7,517			11,357
	Intangible assets	3,071			3,538
	Long-term Investments	—			19,016
	Others	6,042			10,223
	Total assets	$	73,560		$	174,388
	Accrued liabilities	$	18,180		$	34,324
	Amount due to SINA	38,620			1,514
	Amount due to the subsidiaries of the Group	20,933			121,977
	Deferred revenues	8,901			14,117
	Others	768			1,174
	Total liabilities	$	87,402		$	173,106
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Net revenues	$	54,432		$	169,819		$	298,767
	Net income (loss)	$	4,531		$	24,864		$	(4,404	)
		Year Ended December 31,
	2012			2013			2014
	(In thousands)
Net cash provided by (used in) operating activities	$	(5,564	)	$	25,236		$	9,298
Net cash used in investing activities	$	—		$	(3,120	)	$	(2,424	)
Net cash provided by (used in) financing activities	$	5,862		$	(14,498	)	$	(6,965	)
Net increase (decrease) in cash and cash equivalents	$	298		$	7,618		$	(91	)
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 its subsidiary, except for the registered capital of VIE and its subsidiary, amounting to $7.0 million and $15.7 million as of December 31, 2013 and 2014, 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 its 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 advertising and marketing service provided by the VIE to related parties was nil, $49.1 million and $136.6 million for the years ended December 31, 2012, 2013 and 2014, respectively. The total amount of costs and expenses allocated from SINA to the VIE was $42.7 million, $37.2 million and $16.1 million for the years ended December 31, 2012, 2013 and 2014, respectively. The total amount of game platform maintenance services provided by a related party to the VIE was $3.5 million, nil and nil for the years ended December 31, 2012,  2013 and 2014. In December 2013, the VIE purchased all of the equity interest of a related party providing the game platform maintenance services for a consideration of $10.1 million.
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 Memberships and data licensing, as well as trademarks, are also held by Weibo Technology, the WFOE.
The following is a summary of VIE agreements:
Loan Agreements. The Company’s wholly owned subsidiary Weibo Technology has granted interest-free loans to the shareholders 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 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.
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 VIE and the shareholders of the VIE have fully performed their obligations under the above-referred agreements, and (ii) Weibo Technology unilaterally consents to terminate the respective share pledge agreement.
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 $79.2 million and $187.8 million in service fees from the VIE under these agreements for the year ended December 31, 2013 and 2014, respectively, which was determined based on the actual cost incurred for providing such service and the cash position and operation of the VIE. No service fees were charged for the years ended December 31, 2012.
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, the VIE and its 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 its subsidiaries in the combined and consolidated financial statements. The Company’s ability to control its 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 its 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 its VIE will occur as a result of the aforementioned risks and uncertainties is remote.

Significant_Accounting_Policie

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Significant Accounting Policies
Significant Accounting Policies
	2. Significant Accounting Policies
	Basis of presentation and use of estimates
	The preparation of the Group’s combined and consolidated financial statements is in conformity with US GAAP, which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from such estimates. The Group believes the basis of combination and consolidation, revenue recognition, fair value accounting, income taxes, goodwill and other long-lived assets, allowances for doubtful accounts, stock-based compensation, and the determination of the estimated useful lives of assets reflect the more significant judgments and estimates used in the preparation of its combined and consolidated financial statements.
	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 are not attributable, directly or indirectly, to the Company as the controlling shareholder. To reflect the economic interest held by non-controlling shareholders, net income (loss) attributable to the non-controlling ordinary shareholders is recorded as non-controlling interests in the Company’s combined and consolidated statements of comprehensive income (loss). Non-controlling interests are classified as a separate line item in the equity section of the Company’s combined and consolidated balance sheets and have been separately disclosed in the Company’s combined and consolidated financial statements to distinguish the interests from that of the Company.
	Fair value measurements
	Financial instruments
	All financial assets and liabilities are recognized or disclosed at fair value in the combined and 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 related party Alibaba, accounts receivable due from SINA and other related parties, prepaid expenses and other current assets, accounts payable, amount due to SINA, accrued liabilities due to third parties and employees, accrued liabilities due to related parties and deferred revenues approximates fair value because of their short-term nature. See Note 14 Financial instruments for additional information.
	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 stated at cost plus accrued interest.
	Long-term investments
	Long-term investments are comprised of investments in publicly traded and privately held companies. For long-term investments over which we do 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 used the equity method to account for the investment in Weibo Interactive prior to May 2013, when it had significant influence but did not control Weibo Interactive.
	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 and records reductions in carrying values when necessary. Determination of fair value requires significant judgment in the selection of 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 combined and consolidated statements of loss and comprehensive loss.
	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 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, 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 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 the write-down is accounted for as a realized loss charged to 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.
	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 combined and consolidated statements of comprehensive income (loss).
	In a business combination achieved in stages, the Company remeasures its previously held equity interest in the acquiree immediately before obtaining control at its acquisition-date fair value and the re-measurement gain or loss, if any, is recognized in earnings. The determination and allocation of fair values to the identifiable assets acquired, liabilities assumed and noncontrolling interests is based on various assumptions and valuation methodologies requiring considerable judgment from management. The most significant variables in these valuations are discount rates, terminal values, the number of years on which to base the cash flow projections, as well as the assumptions and estimates used to determine the cash inflows and outflows. The Company determines discount rates to be used based on the risk inherent in the related activity’s current business model and industry comparisons. Terminal values are based on the expected life of assets, forecasted life cycle and forecasted cash flows over that period.
	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 $16.4 million, $21.3 million and $21.8 million for the years ended December 31, 2012, 2013 and 2014, 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 VIEs. 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. The quantitative impairment test consists of a comparison of the fair value of goodwill with its carrying value. For reporting units directly applying a quantitative assessment, the goodwill impairment test is quantitatively performed by comparing the fair values of those reporting units to their carrying amounts. The Group adopted the option to apply the qualitative approach to assess its goodwill on the relevant reporting units. 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.
	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 service-based 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.
	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.
	Prior to the IPO, the determination of estimated fair value of Weibo required complex and subjective judgments due to their limited financial and operating history, unique business risks and limited public information on companies in China similar to Weibo. The Group, with the assistance of an independent valuation firm, evaluated the use of two generally accepted valuation approaches. The income approach was used if a revenue model had been established, the market approach was used if information from comparable companies had been available, or a weighted blend of these two approaches was used if more than one was applicable, to estimate the enterprise value for purposes of recording stock-based compensation in connection with employee stock options and recording fair value changes for option liability to Alibaba. For the market approach, the Group selected guideline companies that engaged in a similar line of business with similar growth prospects and that were subject to similar financial and business risks. Prior to the IPO, the income approach was applied when the revenue model for Weibo had been established and projections of revenues, costs and expenses, incremental working capital and capital expenditures became available as the business developed. After the IPO, the closing market price of the underlying shares on the last trading date prior to the grant dates is applied in determining the fair value of the options and RSUs granted. Changes in these estimates and assumptions could materially affect the determination of fair value of stock-based compensation.
	Allowances for doubtful accounts
	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.
	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.
	Other revenues
	The Group generates other 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 Company. 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 the third-party developed 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 has determined that the game developers are the primary obligors for the game-related service given that 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. The Group views the game developers to be its customers, and 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. Accordingly, the Group records game-related revenue, net of predetermined revenue sharing with the game developers.
	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 net of the game developer proceeds 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 began to offer 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.
	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.
	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 tax 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. In November 2011, the Ministry of Finance and the State Administration of Taxation promulgated the Pilot Program for Imposition of Value-Added Tax (“VAT”) to Replace Business Tax (“Pilot Program”). Pursuant to the Pilot Program, a VAT was initially imposed in Shanghai starting from January 1, 2012, to replace the business tax in the transport and shipping industry and some of the modern service industries. Effective September 1, 2012, the Pilot Program was expanded to eight other cities and provinces in China, including Beijing. Beginning from August 1, 2013, the Pilot Program was expanded to all regions in PRC. With the implementation of the Pilot Program, the Group is subject to 6.7% VAT and surcharges and 3% cultural business construction fees for certain parts of its advertising and marketing revenues. Prior to the Pilot Program, the Group was subject to 5.6% business tax and surcharges and 3% cultural business construction fees. The total amount of such taxes on its advertising and marketing revenues for the years ended December 31, 2012, 2013 and 2014 were $4.9 million, $12.5 million and $23.2 million, respectively. For other revenues, the business tax and surcharges were 5.6% before the implementation of the Pilot Program and became 6.7% after switching over to the VAT. The implementation of the Pilot Program has not had a significant impact on the Group’s combined and consolidated statements of loss and comprehensive loss for the years ended December 31, 2013 and 2014.
	Advertising expenses
	Advertising expenses consist primarily of costs for the promotion of corporate image and product marketing, part of which were allocated from SINA (see Note 1 Reorganization). The Group expenses all advertising costs as incurred and classifies these costs under sales and marketing expenses. For the years ended December 31, 2012, 2013 and 2014, the advertising expenses were $23.5 million, $33.2 million and $70.9 million, respectively.
	Product development expenses
	Product development expenses consist primarily of payroll-related expenses and infrastructure cost 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.
	Operating leases
	The Group leases office space under operating lease agreements with initial lease term up to three 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 were 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, 2012, 2013 and 2014, were $1.8 million, $3.2 million and $4.0 million, respectively.
	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. Income tax liability is calculated based on a separate return basis as if the Group had filed separate tax returns before the Reorganization.
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.
Foreign currency
The Group’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 and expenses. Translation gains and losses are recorded in accumulated other comprehensive income or loss as a component of shareholders’ equity (deficit). 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 (expense), net.
Foreign currency translation adjustments included in the Group’s combined and consolidated loss and comprehensive loss for the years ended December 31, 2012, 2013 and 2014 were gain of less than $0.1 million,  loss of $0.4 million and loss of $1.4 million, respectively. 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.
Preferred Shares
The preferred shares have been classified as mezzanine equity instead of permanent equity in the Group’s combined and consolidated financial statements as these preferred shares are contingently redeemable upon the occurrence of a conditional event (i.e. a liquidation event), which is not solely within the control of the Company. See Note 3—Investment in Weibo for further details.
Loss per share
Loss per share is computed in accordance with ASC 260, Earnings per Share. The two-class method is used for computing earnings per share in the event the Group has net income available for distribution. Under the two-class method, net income is allocated between ordinary shares and participating securities based on dividends declared (or accumulated) and participating rights in undistributed earnings as if all the earnings for the reporting period had been distributed. The Company’s convertible preferred shares are participating securities because they are entitled to receive dividends or distributions on an as converted basis. For the periods presented herein, the computation of basic loss per share using the two-class method is not applicable as the Group is in a net loss position and net loss is not allocated to other participating securities, since these securities are not obligated to share the losses in accordance with the contractual terms.
Basic net loss 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 loss per share is computed using the weighted average number of ordinary shares and potential ordinary shares outstanding during the period under treasury stock method. Potential ordinary shares include options to purchase ordinary shares, RSUs and preferred shares, unless they were anti-dilutive. The computation of diluted net loss 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 loss per share.
Segment reporting
In accordance with ASC 280, Segment Reporting, the Group’s chief operating decision maker (“CODM”), the Chief Executive Officer, reviews the combined and 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 other 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 segments are 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, 2013 and 2014, the Group had $496.2 million and $447.1 million in cash and bank time deposits (with terms generally up to twelve months) with large domestic banks in China, respectively. 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.
Accounts receivable, including accounts receivable due from third parties, accounts receivable due from related party Alibaba and accounts receivable due from SINA and other related parties, consist primarily of advertising agencies and direct advertising customers. As of December 31, 2013 and 2014, substantially all accounts receivable were derived from the Group’s China operations. Only Alibaba accounted for over 10% of the Group’s net accounts receivable as of December 31, 2013 and 2014.
Excluding the advertising and marketing revenues from Alibaba, most of the Group’s advertising and marketing revenues are from agencies. The Group’s top 10 advertising agencies in China contributed to 20% and 14% of the Group’s total revenues for the years ended December 31, 2013 and 2014. No customer accounted for over 10% of the Group’s total revenue for the years ended December 31, 2012. Only Alibaba accounted for over 10% of the total revenue for the years ended December 31, 2013 and 2014.
Concentration of foreign currency risks. For the years ended December 31, 2012, 2013 and 2014, the majority of the Group’s revenues derived and expenses incurred were in RMB. As of December 31, 2013 and 2014, the Group’s cash, cash equivalents and short-term investments balance denominated in RMB was $62.1 million and $9.0 million, accounting for 12% and 2% of the Group’s total cash, cash equivalents and short-term investments balance. As of December 31, 2013 and 2014, the Group’s aggregated net accounts receivable balance (including accounts receivable due from third parties, accounts receivable due from related party Alibaba and accounts receivable due from SINA and other related parties) denominated in RMB was $47.3 million and $120.1 million, accounting for almost all of its net accounts receivable balance. As of December 31, 2013 and 2014, the Group’s current liabilities balance denominated in RMB was $56.2 million and $104.8 million, accounting for 15% and 93% of its total current liabilities balance. Accordingly, the Group may experience economic losses and negative impacts on earnings and equity (deficit) as a result of exchange rate fluctuations of RMB. Moreover, the Chinese government imposes controls on the convertibility of 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.
Comprehensive loss
Comprehensive loss is defined as the change in equity of a company during a period from transactions and other events and circumstances excluding transactions resulting from investments from owners and distributions to owners. Comprehensive loss for the periods presented includes net loss and foreign currency translation adjustments.
Recent accounting pronouncements
The FASB issued Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, which changes the threshold for reporting discontinued operations and adds new disclosures. The new guidance defines a discontinued operation as a disposal that “represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results.” The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2014, and interim periods within those annual periods. Entities may “early adopt” the guidance for new disposals. The Group is in the process of evaluating the impact of adoption of this guidance on the combined and combined and consolidated financial statements.
In May 2014, the 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 core principle of the guidance is that an entity should recognize revenues to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps:
	·	Step 1: Identify the contract(s) with a customer.
	·	Step 2: Identify the performance obligations in the contract.
	·	Step 3: Determine the transaction price.
	·	Step 4: Allocate the transaction price to the performance obligations in the contract.
	·	Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation.
For a public entity, the amendments in this ASU are effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. In April 2015, the FASB proposed a one-year delay in the effective date and companies will be allowed to early adopt as of the original effective date..  The Group is in the process of evaluating the impact of adoption of this guidance on the combined and consolidated financial statements.
In June 2014, the FASB issued a new pronouncement which requires that a performance target that affects vesting and that could be achieved after the requisite service period is treated as a performance condition. A reporting entity should apply existing guidance in Topic 718, Compensation—Stock Compensation, as it relates to awards with performance conditions that affect vesting to account for such awards. The performance target should not be reflected in estimating the grant-date fair value of the award. Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered. If the performance target becomes probable of being achieved before the end of the requisite service period, the remaining unrecognized compensation cost should be recognized prospectively over the remaining requisite service period. The total amount of compensation cost recognized during and after the requisite service period should reflect the number of awards that are expected to vest and should be adjusted to reflect those awards that ultimately vest. The requisite service period ends when the employee can cease rendering service and still be eligible to vest in the award if the performance target is achieved. The amendments in this ASU are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted. The Group does not expect the adoption of this guidance will have a significant effect on its financial position, results of operations, or cash flows.
In August 2014, the FASB issued a new pronouncement Presentation of Financial Statements — Going Concern. This standard requires management to evaluate for each annual and interim reporting period whether it is probable that the reporting entity will not be able to meet its obligations as they become due within one year after the date that the financial statements are issued. If the entity is in such a position, the standard provides for certain disclosures depending on whether or not the entity will be able to successfully mitigate its going concern status. This guidance is effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016. Early application is permitted. The Group does not expect the adoption of this guidance will have a significant effect on its financial position, results of operations, or cash flows.
In February 2015, the FASB issued ASU 2015-02, “Consolidation (Topic 810) - Amendments to the Consolidation Analysis”, which provides guidance for reporting entities that are required to evaluate whether they should consolidate certain legal entities. In accordance with ASU 2015-02, all legal entities are subject to reevaluation under the revised consolidation model. ASU 2015-02 is effective for public business entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early adoption is permitted. The Group is currently evaluating the impact on the adoption of ASU 2015-02 to its combined and consolidated financial statements.

Investment_in_Weibo

Investment in Weibo	12 Months Ended
	Dec. 31, 2014
Investment in Weibo
Investment in Weibo
	3. Investment in Weibo
	On April 29, 2013 (“Transaction Date”), Alibaba Group Holding Limited (“Alibaba”) through its wholly owned subsidiary  invested $585.8 million to purchase 30.0 million of preferred shares and 4.8 million of ordinary shares of the Company, representing an ownership interest of 18% on a fully diluted basis. The Company also granted an option to Alibaba to enable it to purchase additional ordinary shares and preferred shares and increase its ownership in Weibo up to 30% on a fully-diluted basis.
	Preferred Shares
	As of the Transaction Date, the fair value of the preferred shares was $481.0 million. The Group determined that both the redemption and conversion features do not meet the criteria under ASC 815 for bifurcation and, therefore, were not accounted for as an embedded derivative. No beneficial conversion feature charge was recognized for the issuance of the preferred shares, as the estimated fair value of the ordinary shares was equal to or less than the conversion price on the date of issuance. The preferred shares have been classified as mezzanine equity instead of permanent equity in the Group’s combined and consolidated financial statements, as these preferred shares are redeemable contingent upon the occurrence of a conditional event (i.e. a liquidation event), which is not solely within the control of the Company. Due to a liquidation event not considered probable, as of the balance sheet dates, no accretion was recorded to adjust the carrying amount of the preferred shares.
	All of the preferred shares were converted to Class A ordinary shares upon the completion of the Group’s initial public offering on April 17, 2014. Immediately prior to the initial public offering, the Company’s preference shares comprised of the following:
	Issuance Date	Shares outstanding	Carrying Amount
			(In thousands)
	April 29, 2013	30,046,154	$	479,612
	Prior to the automatic conversion to ordinary share upon the Company’s initial public offering on April 17, 2014, the preference shares were entitled to certain preferences with respect to conversion, redemption, dividends and liquidation. The holders of preference shares were entitled to vote together with the holders of ordinary shares, and not as a separate class, on all matters submitted to a vote of the shareholders of the Company, on an as-if-converted basis.
	Ordinary Shares
	The ordinary shares held by Alibaba, recognized at an initial fair value of $54.2 million as of the Transaction Date, were purchased from the Group’s employees or from the Company for vested employee options repurchased. In order to facilitate the transaction, the Company issued ordinary shares to Alibaba on the Transaction Date and then repurchased the 3.5 million vested options from employees subsequent to the Transaction Date. The consideration for both the ordinary shares and vested options were paid to the Company first and then paid to the employees subsequently. The difference between the proceeds employees received and the fair value of the shares or vested options sold was considered to be compensation for past services in accordance with ASC 718-20. Therefore, a stock-based compensation of $27.1 million was recorded for the year ended December 31, 2013.
	Option Liability
	The Company granted an option to Alibaba to enable it to purchase additional ordinary shares and increase its ownership in the Company up to 30% on a fully-diluted basis. The call option shall expire immediately upon the earlier of the consummation of (i) any sale of shares by Alibaba of more than 25%, determined in the aggregate with all prior sales, of the acquired shares and (ii) the full exercise of the call option. Alibaba has the right to exercise the option, in whole or in part, at any time, commencing on the Transaction Date and ending on the consummation of a qualified IPO of Weibo. The exercise price of the option shall be equal to the lower of (i) an amount that represents a 15% discount to the IPO offering price per ordinary share in a qualified IPO offering and (ii) a price per ordinary share that implies an equity valuation (exclusive of the purchase price to be paid by Alibaba for these ordinary shares) of $5.5 billion for the Company on a fully diluted basis.
	In accordance with ASC subtopic 815-10, the option is deemed legally detachable and separately exercisable from the preferred and ordinary shares and, thus, accounted for as a freestanding instrument. As the strike price of the call option may be adjusted by the occurrence of a qualified IPO of Weibo, if any, it is not considered indexed to Weibo’s own stock. Accordingly, the call option was recorded as an investor option liability valued at $50.6 million as of the Transaction Date. For the year ended December 31, 2012, 2013 and 2014,  nil, $21.1 million of income and $47.0 million of losses, respectively, was recognized based on a subsequent change in fair value in the Group’s combined and consolidated statements of loss and comprehensive loss. See Note 14 for further details.
	The Group used the income approach to derive the fair value of the preferred shares, ordinary shares and the option granted to Alibaba as of the Transaction Date and prior to IPO. When using the income approach, the Group applied the discounted cash flow analysis based on the Group’s projected cash flow using management’s best estimate as of the Transaction Date. Determination of the estimated fair values requires complex and subjective judgments due to the Company’s limited financial and operating history, unique business risks and limited public information on companies in China similar to the business of the Group. Changes in these estimates and assumptions could materially impact the Group’s financial position and results of operations. The option was recorded at fair value as of the grant date as option liability in the combined and consolidated balance sheets and is marked to market at each reporting period end, which requires an assessment of the probability weight for each exercise scenario.
	Immediately prior to the exercise of the option, the fair value of the investor option liability was approximately $76.5 million, with $47.0 million of losses recognized in the Group’s combined and consolidated statements of loss and comprehensive loss in 2014. Alibaba fully exercised its option to increase its ownership in the Company to 30% on a fully diluted basis upon the IPO and acquired 29,990,778 Class A ordinary shares, which consists of (i) 21,067,300 shares acquired from SINA at a price that represents a 15% discount to the IPO price of the Company, (ii) 2,923,478 shares acquired from the Company at a price that represents a 15% discount to the IPO price through a concurrent private placement and (iii) 6,000,000 shares purchased from the Company at the IPO price. As part of a series of the transaction, the Company repurchased 2,923,478 ordinary shares from SINA with the US$42.2 million proceeds from the issuance of ordinary shares to Alibaba in the concurrent private placement. Among the acquired shares by Alibaba, 23,990,778 shares were purchased from SINA at a price representing 15% discount to its IPO price and 6,000,000 shares were purchased from the Company in the public offering at the IPO price. The discount of US$ 61.2 million borne by SINA on behalf of Weibo were considered as a deemed contribution from the shareholder. As Alibaba’s decision to waive the discount for the newly issued 6,000,000 Class A ordinary shares was motivated by its position as principle shareholder, the discount of US$15.3 million was also considered as a deemed contribution from the shareholder.
	Amount due to SINA
	In April 2013, the Group agreed to repay SINA for the cost of developing its business plus applicable interest payments. The interest on amount due to SINA is calculated based on actual spending incurred by SINA for the development of Weibo’s business at each period end. The combined and consolidated statements of loss and comprehensive loss reflect a charge for interest on the amount due to SINA, as well as on the amounts included as accrued liabilities due to SINA at prevailing market interest rates by reference to the three-month time deposit rate of The People’s Bank of China, which ranged from 2.55% to 3.05%. The loans are repayable upon demand. There is no written agreement signed between SINA and Weibo and there are no fixed payment terms for the loan. In accordance with the agreements for the Alibaba Transaction, the Group is liable for a $250.0 million loan payable to SINA as of April 29, 2013, plus applicable interest payments and any additional outlays subsequent to the Transaction Date. On April 29, 2013, $8.5 million in interest due to SINA was waived, which was recorded as deemed contribution from SINA in the equity section of the combined and consolidated balance sheets. The outstanding loan balance due to SINA was settled after the IPO with proceeds raised from the IPO. The $1.7 million amount due to SINA as of December 31, 2014 represent the unpaid amount related to the allocated expenses from SINA.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents and Short-term Investments	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents and Short-term Investments
Cash, Cash Equivalents and Short-term Investments
	4. Cash, Cash Equivalents and Short-term Investments
	Cash, cash equivalents and short-term investments consist of the following:
		As of December 31,
		2013		2014
		(In thousands)
	Cash and cash equivalents:
	Cash	$	13,332	$	53,512
	Cash equivalents:
	Bank time deposits	233,104		229,950
		246,436		283,462
	Short-term investments:
	Bank time deposits	252,342		166,414
	Total cash, cash equivalents and short-term investments	$	498,778	$	449,876
	The carrying amounts of cash, cash equivalents and short-term investments approximate fair values. There was no material interest income recognized during the year ended December 31, 2012. Interest income for the year ended December 31, 2013 and 2014 was $3.8 million and $8.3 million, respectively. The maturity dates of the bank time deposits were within one year.

Longterm_Investments_Acquisiti

Long-term Investments Acquisition	12 Months Ended
	Dec. 31, 2014
Long-term Investments and Acquisition
Long-term Investments and Acquisition
	5. Long-term Investments and Acquisition
	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			Total
								Securities
		(In thousands)
	Balance at January 1, 2012	$	—		$	4,905		$	—		$	4,905
	Loss from long-term investments	—			(1,340		)	—			(1,340		)
	Balance at December 31, 2012	$	—		$	3,565		$	—		$	3,565
	Loss from long-term investments	—			(1,236		)	—			(1,236		)
	Investments made	5,500			4,635			—			10,135
	Remeasurement gain upon obtaining control	—			3,116			—			3,116
	Transfer from long-term investments to a wholly owned subsidiary	—			(10,080		)	—			(10,080		)
	Balance at December 31, 2013	$	5,500		$	—		$	—		$	5,500
	Investments made	26,670			—			15,096			41,766
	Unrealized loss	—			—			(2,067		)	(2,067		)
	Balance at December 31, 2014	$	32,170		$	—		$	13,029		$	45,199
	Investments in marketable securities are held as available-for-sale and reported at fair value, which totaled nil and $13.0 million as of December, 2013 and 2014, respectively. The Group reviews its available-for-sale investment regularly and determine if an investment is other-than-temporarily impaired due to changes in quoted market price or other impairment indicators. As of December 31, 2014, no impairment indicators were noted on the Group’s long-term investments.
	In May 2013, SINA acquired the remaining 45% equity interest in Weibo Interactive, an online-game platform company that it had accounted for under the equity method of accounting, for a consideration of $4.6 million. In accordance with ASC805 regarding a business combination achieved in stages, SINA’s previously held 55% equity interest were remeasured to fair value at the date of acquisition using the discounted cash flow method, which resulted in a $3.1 million remeasurement gain upon obtaining control. SINA hired an independent valuation firm to assist management in valuing its previously held equity interest in Weibo Interactive as of the acquisition date. SINA began to consolidate Weibo Interactive’s financial statements from June 1, 2013. Goodwill arising from this transaction primarily represents the expected synergies from combining the complementary operations of Weibo Interactive with the Group. Total identifiable intangible assets acquired upon acquisition mainly included a customer list of $2.1 million, game platform technology of $1.0 million and non-compete agreement of $0.5 million, with an estimated average weighted useful life between two to five years.
	Consideration for Weibo Interactive was allocated on the acquisition date based on their fair value of the assets acquired and the liabilities assumed as follows:
		As of acquisition date
		(In thousands)
	Cash consideration for the remaining 45% equity interest	$	4,635
	Fair value of previously held 55% equity interest	5,445
	Total consideration	10,080
	Tangible assets	98
	Identifiable intangible assets acquired	3,560
	Liabilities assumed	(1,095		)
	Goodwill	7,517
	Total consideration	$	10,080
	In connection with the Reorganization, SINA transferred 100% equity interest in Weibo Interactive to the Group in December 2013 for a consideration of $10.1 million (Note 1). The amounts recognized in the Group’s financial statements reflected the transferred assets and liabilities at SINA’s historical cost for all periods presented as this is a transaction between entities under common control. The acquisition completed in May 2013 was not material to the Group’s combined and consolidated financial statements, and, therefore, pro forma disclosure is not required.
	In October 2014, the Group acquired an 84% equity interest in Shanghai Gametree Information Technology Co. Ltd,. (“Gametree”), a game developer for a consideration of $3.1 million and began to consolidate its financial results since October 1, 2014. The Group hired an independent valuation firm to assist management in valuing the equity interest acquired by the Group. Goodwill arising from this transaction primarily represents the expected synergies from combining the operations of game developer with the Group, which are complementary to each other. Total identifiable intangible assets acquired upon acquisition were the existing game technology amounting to $1.7 million, which have an estimated useful life approximates 4.3 years. The impact of the game developer’s  financial results since the acquisition date included in the combined and consolidated financial statements of the Group was immaterial. The acquired business is also not material to the Group’s financial statements and, thus, a presentation of pro-forma financial information for the business combination is not required.
	Consideration for the purchase was allocated on the acquisition date based on the fair value of the assets acquired and the liabilities assumed as follows:
		As of acquisition date
		(In thousands)
	Cash consideration	$	3,062
	Non-controlling interests	292
	Total consideration	3,354
	Tangible assets	1,518
	Identifiable intangible assets acquired	1,688
	Liabilities assumed	(3,692		)
	Goodwill	3,840
	Total consideration	$	3,354
	The following sets forth the changes in the Group’s goodwill by segment:
		Advertising &			Other			Total
		Marketing
		(In thousands)
	Balance as of January 1, 2013	$	—		$	—		$	—
	Acquisition of Weibo Interactive	—			7,517			7,517
	Balance as of December 31, 2013	$	—		$	7,517		$	7,517
	Acquisition of game developer	—			3,840			3,840
	Others	—			295			295
	Balance as of December 31, 2014	$	—		$	11,652		$	11,652
	As of December 31, 2014, 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 assessment, the Group determined that it was not necessary to perform a quantitative goodwill impairment test and concluded that no impairment indicators on its goodwill were noted during the period presented.
	As of December 31, 2014, the Group’s intangible assets totaling $3.5 million, mainly consisted of acquired intangible assets, including game-related platform technology, game-user base and customer contracts. The amortization expensed for the year ended December 31, 2013 and 2014 was $0.2 million and $1.2 million, respectively. As of December 31, 2014, estimated amortization expenses for future periods are expected to be as follows:
	Year Ended December 31,	(In thousands)
	2015	$	1,498
	2016	769
	2017	688
	2018	584
	2019 and thereafter	—
	Total expected amortization expense	$	3,539

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
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. The Company granted options equivalent to approximately 1.3%, 1.7% and nil of the Company’s ordinary shares on a fully diluted basis for the years ended December 31, 2012, 2013 and 2014, respectively. Fair value of options granted, which was estimated at grant date, for the years ended December 31, 2012, 2013 and 2014 was $3.6 million, $16.9 million and nil, respectively.
	In March 2014, the Company adopted the 2014 Share Incentive Plan (the “2014 Plan”), which was initially funded by the remaining 4.6 million shares from the 2010 Plan plus an addition of 1.0 million shares. On January 1, 2015, shares in the 2014 Plan will be allowed a one-time increase in an amount equal to 10% of the total number of Weibo shares issued and outstanding on a fully-diluted basis as of December 31, 2014. The Company intends to use such share incentive plan, which has a term of ten years, to continue 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,
		2012			2013			2014
		(In thousands)
	Cost of revenues	$	201		$	4,253		$	755
	Sales and marketing	330			6,150			1,583
	Product development	638			9,209			4,392
	General and administrative	668			11,630			7,049
		$	1,837		$	31,242		$	13,779
	Stock based compensation related to the grants were amortized generally over four years on a straight-line basis with $1.8 million, $4.1 million and $13.8 million expensed for the years ended December 31, 2012, 2013 and 2014, respectively. Stock-based compensation for the year ended December 31, 2013 included a $27.1 million expense, which is the difference between the purchase price and the fair value of ordinary shares or vested options purchased from employees in connection with the Alibaba transaction (Note 3).
	Stock Options
	The Group uses the Black-Scholes option pricing model to estimate the fair value of stock options. The assumptions used to value the Company’s option grants were as follows:
		Year Ended December 31,
		2012		2013		2014*
	Stock options:
	Expected term (in years)	3.5 - 4.8		3.5 - 4.8		N/A
	Expected volatility	60% - 63%		54% -61%		N/A
	Risk-free interest rate	0.4% - 0.8%		0.5% - 1.2%		N/A
	Expected dividend yield	—		—		—
	* No stock options were granted in 2014.
	Expected term represents the weighted average period of time that stock-based awards granted are expected to be outstanding taking consideration of historical exercise patterns. Due to the lack of industry comparison and comparable historical exercise pattern, the Company used the simplified method to calculate the expected term. Expected volatilities are based on historical volatilities of comparable companies’ ordinary shares over the respective expected term of the stock-based awards. Risk-free interest rate is based on US Treasury zero-coupon issues with maturity terms similar to the expected term on the stock-based awards. The Company does not anticipate paying any cash dividends in the foreseeable future.
	The following table sets forth a summary of the number of shares available for issuance:
		Shares Available
		(In thousands)
	December 31, 2011	6,728
	Granted	(2,175	)
	Cancelled/expired/forfeited	908
	Repurchased	2,625
	December 31, 2012	8,086
	Granted*	(4,772	)
	Cancelled/expired/forfeited	1,157
	Repurchased	177
	December 31, 2013	4,648
	Addition (2014 plan)	1,000
	Granted*	(2,951	)
	Cancelled/expired/forfeited	41
	December 31, 2014	2,738
	*In 2013, 0.8 million restricted share units, equivalent to 1.4 million option shares, and 3.4 million stock options were granted under the 2010 plan. In 2014,  3.0 million restricted share units and no stock option were granted under the 2014 plan.
	The following table sets forth the summary of option activities under the Company’s stock option program:
		Options		Weighted Average			Weighted Average		Aggregate
		Outstanding		Exercise Price			Remaining		Intrinsic Value
							Contractual Life
		(In thousands)					(In years)		(In thousands)
	December 31, 2011	28,272		$	0.41		5.5		$	82,726
	Granted	2,175		$	3.34
	Exercise	(3,445	)	$	0.36
	Cancelled/expired/forfeited	(908	)	$	0.6
	Repurchased	(2,625	)	$	0.36
	December 31, 2012	23,469		$	0.69		4.6		$	60,226
	Granted	3,372		$	3.38
	Exercise	(3,449	)	$	0.38
	Cancelled/expired/forfeited	(1,157	)	$	2.49
	Repurchased	(3,674	)	$	0.45
	December 31, 2013	18,561		$	1.17		4.3		$	239,975
	Granted	—		$	—
	Exercise	(3,697	)	$	0.52
	Cancelled/expired/forfeited	(534	)	$	2.84
	Repurchased	—		$	—
	December 31, 2014	14,330		$	1.28		3.2		$	185,684
	Vested and expected to vest as of December 31, 2013	18,261		$	1.14		4.3		$	236,716
Exercisable as of December 31, 2013	8,957		$	0.48		3.7		$	122,026
Vested and expected to vest as of December 31, 2014	14,261		$	1.27		3.2		$	184,937
Exercisable as of December 31, 2014	11,446		$	0.76		2.7		$	154,235
The total intrinsic value of options exercised for the years ended December 31, 2012, 2013 and 2014 was $10.3 million,  $37.3 million and $65.7 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 of December 31, 2013, the estimated fair value of the Company’s ordinary shares was $14.10, which was determined with the assistance of an independent valuation firm. As reported by the NASDAQ Global Selected Market, the Company’s ending stock price as of December 31, 2014 was $14.24. Cash received from the exercise of stock option during the year ended December 31, 2012, 2013 and 2014 was nil, $1.0 million and $1.5 million, respectively.
As of December 31, 2013 and 2014, unrecognized compensation cost, adjusted for estimated forfeitures, related to non-vested stock options granted to the Group’s employees and directors was $16.4 million and $11.3 million, respectively. Total unrecognized compensation cost is expected to be recognized over a weighted-average period of 2.2 years and may be adjusted for future changes in estimated forfeitures.
Information regarding stock options outstanding is summarized below:
Range of Exercise Prices	Options		Weighted			Options		Weighted		Weighted Average
	Outstanding		Average			Exercisable		Average		Remaining
			Exercise Price					Exercise Price		Contractual Life
	(In thousands)					(In thousands)				(In years)
As of December 31, 2013
$0.36 - 0.41	12,571		$	0.36		7,989		$	0.36	3.7
$0.96 - 1.80	1,324		$	1.14		830		$	1.14	4.3
$3.25 - $3.36	2,822		$	3.30		138		$	3.26	5.6
$3.43 - $3.50	1,844		$	3.48		—		$	—	6.6
	18,561		$	1.17		8,957		$	0.48	4.3
As of December 31, 2014
$0.36 - 0.41	9,337		$	0.37		9,337		$	0.37	2.3
$0.96 - 1.80	844		$	1.19		764		$	1.18	3.1
$3.25 - $3.36	2,542		$	3.29		1,345		$	3.30	4.8
$3.43 - $3.50	1,607		$	3.48		—		$	—	5.5
	14,330		$	1.28		11,446		$	0.76	3.2
Restricted Share Units
The following table sets forth a summary of restricted share unit activities:
	Shares		Weighted-Average
	Granted		Grant Date
			Fair Value
	(In
	thousands)
December 31, 2013	800		$	13.19
Awarded	2,951		$	17.11
Vested	(203	)	$	13.19
Cancelled	(41	)	$	17.23
December 31, 2014	3,507		$	16.44
As of December 31, 2014, unrecognized compensation cost, adjusted for estimated forfeitures and related to non-vested, service-based RSUs granted to the Company’s employees and non-employee directors, was $47.7 million. This cost is expected to be recognized over a weighted-average period of 3.5 years.  The total fair value based on the vesting date of the restricted  share units vested was nil and $2.7 million for the years ended December 31, 2013 and 2014 respectively.

Other_Balance_Sheet_Components

Other Balance Sheet Components	12 Months Ended
	Dec. 31, 2014
Other Balance Sheet Components
Other Balance Sheet Components
	7. Other Balance Sheet Components
		As of December 31,
		2012		2013			2014
				(In thousands)
	Accounts receivable, net:
	Due from third parties			$	27,189		$	39,277
	Due from SINA and other related parties			2,058			18,648
	Due from related party Alibaba			21,299			64,725
	Total gross amount			$	50,546		$	122,650
	Allowance for doubtful accounts:
	Balance at the beginning of the year	—		(897		)	(3,242		)
	Additional provision charged to expenses	(897	)	(2,345		)	(2,138		)
	Write-off	—		—			2,940
	Balance at the end of the year	(897	)	(3,242		)	(2,440		)
				$	47,304		$	120,210
	Prepaid expenses and other current assets:
	Rental and other deposits			$	3,244		$	3,319
	Current deferred tax assets			744			18
	Input VAT			—			1,526
	Prepayment for long-term investments			495			1,942
	Advertising prepayment			—			3,936
	Prepayment to outsource service providers			—			1,730
	Prepayment for license fee			—			1,872
	Others			1,210			1,761
				$	5,693		$	16,104
	Property and equipment, net:
	Computers and equipment			$	74,843		$	89,069
	Leasehold improvements			4,340			4,944
	Furniture and fixtures			1,490			2,052
	Others			392			730
				81,065			96,795
	Less: Accumulated depreciation			(45,363		)	(65,921		)
				$	35,702		$	30,874
	Accrued liabilities*:
	Payroll and welfare			$	7,336		$	19,686
	Amounts owed on option/share repurchase			12,073			1,203
	Content fees (including amounts due to related parties of $486 and nil as of December 31, 2013 and 2014)			572			1,005
	Marketing expenses (including amounts due to related parties of $3,021 and 5,786 as of December 31, 2013 and 2014)			11,288			19,806
	Internet connection costs			1,591			6,834
	Employee payroll withholding taxes			3,950			3,547
	Sales rebates			7,007			14,126
	Advertisement production costs			2,774			—
	Professional fees			912			3,138
	Revenue share			3,097			3,057
	VAT and other tax payable			702			6,629
	Payable to other service providers			1,800			1,074
	Payable to outsourced service providers			671			1,375
	Others			2,641			5,998
				$	56,414		$	87,478
	* Include amounts due to third parties, employees and related parties.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes
Income Taxes
	8. Income Taxes
	The Company is registered in the Cayman Islands and mainly has operations in two tax jurisdictions—the PRC and Hong Kong.
	The components of loss before income taxes are as follows:
		Year Ended December 31,
		2012			2013			2014
		(In thousands, except percentage)
	Loss before income tax expenses	$	(104,037	)	$	(37,844	)	$	(61,506	)
	Loss from non-China operations	$	(2,950	)	$	(13,341	)	$	(54,073	)
	Loss from China operations	$	(101,087	)	$	(24,503	)	$	(7,433	)
	Income tax expenses (benefits) applicable to China operations	$	(1,551	)	$	271		$	1,128
	Effective tax rate for China operations	1.5		%	(1.1		)%	(15.2		)%
	With the exception of a $47.0 million loss in 2014 from the change in fair value of investor option liability which was recorded in non-China operations, the Company generated the majority of its operating loss from the PRC operations and has recorded income tax provisions (benefits) for the periods presented. Income tax liability is calculated based on a separate return basis, as if the Group had filed separate tax returns before the Reorganization.
	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, 2014, the Company’s Hong Kong subsidiary had approximately $2.1 million of net operating loss carry forwards, which can be carried forward indefinitely to offset future taxable income. As of December 31, 2014, deferred tax assets for Weibo HK consists mainly of net operating loss carry forwards, 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% if they are not eligible for any preferential tax treatment. On February 22, 2008, relevant governmental regulatory authorities released 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 to a rate of 12.5% for the subsequent three years. The Group’s WFOE qualifies as a software enterprise and, thus, can enjoy the relevant tax holiday starting in its first profitable year.
	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 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 us. 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 the Hong Kong subsidiary. 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, 2013 and 2014, the Group did not record any withholding tax for its WFOE and VIE, as the WFOE and VIE companies were still in accumulative deficit position. The net operating loss will start to expire in 2017 if not utilized.
	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 subsidiary and VIE:
		Years Ended December 31,
		2012			2013			2014
		(In thousands)
	Deferred tax expenses (benefits)	$	(1,551	)	$	271		$	866
	Current income tax expenses	—			—			262
	Income tax expenses (benefits)	$	(1,551	)	$	271		$	1,128
	Reconciliation of the differences between statutory tax rate and 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,
		2012		2013		2014
	Statutory EIT rate	(25.0	)%	(25.0	)%	(25.0	)%
	Permanent differences	3.2	%	0.6	%	3.0	%
	Change in valuation allowance	23.3	%	23.3	%	6.8	%
	Effective tax rate for China operations	1.5	%	(1.1	)%	(15.2	)%
	The provisions for income taxes for the years ended December 31, 2012, 2013 and 2014 differ from the amounts computed by applying the statutory EIT rate primarily due to full utilization of net operating loss of Weimeng, as it was in profitable position in 2014. There is no effect of tax holiday related to China operations due to its accumulative loss status.
	Deferred tax assets and liabilities
	The following table sets forth the significant components of deferred tax assets and liabilities for the Group:
		As of December 31,
		2013			2014
		(In thousands)
	Deferred tax assets:
	Net operating loss carry forwards	$	49,800		$	42,096
	Less: valuation allowance	(48,577		)	(42,065		)
	Net deferred tax assets	$	1,223		$	31
	Including-Current deferred tax assets	744			18
	-Non-current deferred tax assets	479			13
	Deferred tax liabilities:
	Acquired intangible assets	$	768		$	873
	Total deferred tax liabilities	$	768		$	873
	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. Historically, deferred tax assets were valued using the statutory rate of 25%. As of December 31, 2013, the Group had net operating loss carry forwards totaling $199.2 million, of which $194.4 million was provided with valuation allowance and the remaining $4.8 million is expected to be utilized prior to expiration. As of December 31, 2014, the Group had net operating loss carry forwards totaling $168.3 million, which full valuation allowance was provided for. As of December 31, 2014, the net operating loss carry forwards will expire, if unused, in the year ending December 31, 2018 through December 31, 2019.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
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 (Post April 29, 2013).
	Weibo Interactive		Investee accounted for under the equity method until May 2013 and wholly owned under common control thereafter.
	The following sets forth significant related party transactions with the Company:
			Year Ended December 31,
			2012		2013		2014
			(In thousands)
	Transactions with SINA
	Deemed contribution from SINA(1)		$	—	$	13,092	$	61,176
	Legal transfer of Weibo Interactive and recognition of due to SINA(2)		$	—	$	10,080	$	—
	Costs and expenses allocated from SINA(3)		$	43,960	$	44,305	$	42,360
	Interest expense on amount due to SINA		$	4,923	$	6,709	$	2,838
	Repayment of amount due to SINA(4)		$	—	$	159,816	$	276,614
		-1		The $13.1 million in deemed contribution from SINA for the year ended December 31, 2013 included $4.6 million related to the step-up acquisition of Weibo Interactive in May 2013 and $8.5 million in interest expensed waived (Note 1). The $61.2 million in deemed contribution from SINA for the year ended December 31, 2014 represents the discount borne by SINA upon the settlement of investor options (Note 3).
		-2		In connection with the Reorganization, SINA transferred 100% equity interest in Weibo Interactive to the Group in December 2013 for a consideration of $10.1 million (Note 1).
		-3		Costs and expenses allocated from SINA represent the charge for certain services provided by SINA’s affiliates and charged to the Company using actual cost allocation based on proportional utilization (Note 1). In addition to the allocated costs and expenses, SINA also billed $15.1 million for other costs and expenses associated with Weibo business.
		-4		For the year ended December 31, 2014, the Company repaid approximately $276.6 million for the loan and relevant interests to SINA (Note 3).
			Year Ended December 31,
			2012		2013		2014
			(In thousands)
	Transactions with Alibaba
	Advertising and marketing services provided to Alibaba		$	—	$	49,135	$	107,587
	Deemed contribution from Alibaba(5)		$	—	$	—	$	15,300
		-5		The $15.3 million for the year ended December 31, 2014, represents the discount borne by Alibaba upon the settlement of investor options (Note 3).
	On April 29, 2013, affiliated entities of SINA, including the Group’s subsidiary, formed a strategic alliance 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’s users. The strategic alliance was entered into on a separate agreement from those relating to the investment in Weibo by Alibaba. For the year ended December 31, 2013 and 2014, the Group recorded advertising and marketing services revenue from Alibaba amounting to $49.1 million and $107.6 million, respectively.
	The following sets forth the outstanding balance due to or from related parties:
			As of December 31,
			2013		2014
			(In thousands)
	Amount due to SINA		$	267,722	$	1,717
	Accounts receivable due from SINA(6)		$	1,830	$	3,151
	Accounts receivable due from Alibaba		$	21,299	$	64,725
	Accrued liabilities due to SINA(6)		$	3,507	$	—
		-6		The Group settles customer and supplier balances with SINA when the third-parties settle such amount with SINA. Any uncollectible losses arising from the accounts receivable due from SINA are passed on to the Group.
	For the year ended December 31, 2012 and 2013, the Group received game platform maintenance service from Weibo Interactive amounting to $3.5 million and nil, respectively. The Group took control of Weibo Interactive in June, 2013. For the year ended December 31, 2012, 2013 and 2014, advertising and marketing revenues generated from other related parties were nil, $2.3 million and $27.6 million, and other revenues from other related parties were nil, nil and $1.5 million, respectively. For the year ended December 31, 2012, 2013 and 2014, the Group received promotional services from other related parties approximately amounting to nil, $0.9 million and $11.2 million, respectively. For transactions with other related parties, no single transaction was material for the combined and consolidated financial statements. As of December 31, 2013 and 2014, the amount due from other related parties was nil and $15.4 million, respectively. As of December 31, 2013 and 2014, the amount due to other related parties was nil and $5.8 million, respectively. No single outstanding balance was material for the combined and consolidated financial statements.

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2014
Employee Benefit Plans
Employee Benefit Plans
	10. Employee Benefit Plans
	China Contribution Plan
	The Company’s subsidiary, VIE and its 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 bureau 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, 2012, 2013 and 2014, the Group’s total contribution was $14.0 million, $18.3 million and $27.2 million, respectively.

Loss_Per_Share

Loss Per Share	12 Months Ended
	Dec. 31, 2014
Loss Per Share
Loss Per Share
	11. Loss Per Share
	Basic net loss per share is computed using the weighted average number of the ordinary shares outstanding during the period. Options, RSUs and preferred shares 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, 2012, 2013 and 2014, options to purchase ordinary shares and RSUs that were anti-dilutive and excluded from the calculation of diluted net loss per share were 23.5 million, 52.6 million, and 17.8 million, respectively. For the years ended December 31, 2012, 2013 and 2014, preferred shares convertible into ordinary shares that were anti-dilutive and excluded from the calculation of diluted net loss per share of Weibo were nil, 30.0 million and nil, respectively.
	For periods prior to the IPO and where Weibo was profitable, the preferred shares held by Alibaba were considered participating securities and, therefore, all profits of Weibo were allocated to ordinary shares and participating securities based on their dividend rights, as if all of the earnings for the period had been distributed. Considering that the holder of preferred shares has no contractual obligation to fund the losses of the Group in excess of the initial investment, the Group believes that in applying the two-class method of calculating EPS in accordance with ASC 260-10 in periods during which the Group recognized losses, any losses from the Group should not be allocated to the preferred shares, since the preferred shares were not obligated to share the losses in accordance with the contractual terms.
	The following table sets forth the computation of basic and diluted net loss per share for the periods indicated:
		Year Ended December 31,
		2012			2013			2014
		(In thousands, except per share data)
	Basic net loss per share calculation:
	Numerator:
	Net loss attributable to ordinary shareholders	$	(102,486	)	$	(38,115	)	$	(63,378	)
	Denominator:
	Weighted average ordinary shares outstanding	140,831			146,820			186,878
	Basic net loss per share attributable to ordinary shareholders	$	(0.73	)	$	(0.26	)	$	(0.34	)
	Diluted net loss per share calculation:
	Numerator:
	Net loss attributable for calculating diluted net loss per share	$	(102,486	)	$	(38,115	)	$	(63,378	)
	Denominator:
	Weighted average ordinary shares outstanding	140,831			146,820			186,878
	Weighted average ordinary shares equivalents:
	Shares used in computing diluted net loss per share attributable to ordinary shareholders	140,831			146,820			186,878
	Diluted net loss per share attributable to ordinary shareholders	$	(0.73	)	$	(0.26	)	$	(0.34	)

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
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 other 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 the Group’s long-lived assets are substantially all located in the PRC and substantially all the Group’s revenues are derived from within the PRC, no geographical segments are presented.
	The following is a summary of the Group’s revenues:
	Revenues	Advertising & Marketing		Other		Total
		(In thousand)
	Year ended December 31, 2012	$	51,049	$	14,880	$	65,929
	Year ended December 31, 2013	$	148,426	$	39,887	$	188,313
	Year ended December 31, 2014	$	264,782	$	69,390	$	334,172

Profit_Appropriation_and_Restr

Profit Appropriation and Restricted Net Assets	12 Months Ended
	Dec. 31, 2014
Profit Appropriation and Restricted Net Assets
Profit Appropriation and Restricted Net Assets
	13. Profit Appropriation and Restricted Net Assets
	The Company’s subsidiary, the VIE and the 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 subsidiary have to make appropriations from its 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 its 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 register 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, 2013, no reserves were made to non-distributable reserve funds by the Group as its subsidiary, VIE and its subsidiaries were at an accumulated deficit position. As of December 31, 2014, the Group accrued approximately $0.1 million in the reserve fund, as Weimeng had fully utilized its accumulated deficit and became profitable since 2014.
	Under the PRC laws and regulations, the subsidiary, the VIE and the 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 combined and consolidated net assets as of December 31, 2014. Even though the Group currently does not require any such dividends, loans or advances from the PRC subsidiary and VIE for working capital and other funding purposes, the Group may in the future require additional cash resources from the PRC subsidiary, 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. As of December 31, 2014, net assets subject to restriction for the Group amounted to $163.0 million.

Financial_Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2014
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, 2013 and 2014:
		Fair Value Measurements
		(in thousands)
		Total			Quoted Prices in		Significant Other		Significant
					Active Market		Observable Inputs		Unobservable Inputs
					for Identical Assets		(Level 2)		(Level 3)
					(Level 1)
	As of December 31, 2013:
	Bank time deposits*	$	485,446		$	—	$	485,446	$	—
	Investor option liability	(29,504		)	—		—		(29,504		)
	Total	$	455,942		$	—	$	485,446	$	(29,504	)
	As of December 31, 2014:
	Bank time deposits*	$	396,364		$	—	$	396,364	$	—
	Available-for-sale securities**	13,029			13,029		—		—
	Total	$	409,393		$	13,029	$	396,364	$	—
	*Included in cash and cash equivalents and short-term investments on the Group’s combined and consolidated balance sheets.
	** Included in long-term investments.
	Recurring
	The Group measures bank time deposits, available-for-sale securities and investor option liability at fair value on a recurring basis.
	The option liability, which enabled Alibaba to purchase additional ordinary shares and increase its ownership in Weibo up to 30% on a fully-diluted basis (Note 3), was measured using significant unobservable inputs (Level 3) when determining its fair value as of December 31, 2013. The Group utilized the Binomial option pricing model to determine the fair value of the option liability. Estimates of the volatility for the option pricing model were based on the volatility of ordinary shares of a group of comparable, publicly-traded companies. Estimates of expected life were based on the estimated time to liquidation events, and in particular, estimates regarding the timing of a qualified IPO, the likelihood that the Company would undertake a liquidation event other than a qualified IPO, as well as assumptions regarding whether Alibaba would choose to sell off more than 25% of its shares in the Company and, if so, when. Accordingly, the weighted time period for the expiration of the option liability was estimated at 1.4 years. The risk-free interest rate was based on the U.S. Treasury yield for a term consistent with the estimated expected life. The key inputs used in option liability valuation as of December 31, 2013 were as follows:
		As of
		December 31, 2013
	Expected dividend yield	—
	Risk-free interest rate	0.30		%
	Expected volatility	53		%
	Expected life (in years)	1.40
	Fair value per ordinary share	$	14.10
	Determination of these unobservable inputs requires complex and subjective judgments due to the limited financial and operating history of the Company, unique business risks and limited public information on companies in China similar to the business of the Company. Changes in these inputs might result in a significantly higher or lower fair value measurement and materially impact the Company’s financial position and results of operations.
	The option liability was initially recorded as an investor option liability valued at $50.6 million as of the Transaction Date. Immediately prior to the exercise of the option, the fair value of investor option liability was $76.5 million. For the year ended December 31, 2013 and 2014,  $21.1 million of income and $47.0 million of losses was recognized as subsequent change in fair value when marked to market in the Group’s combined and consolidated statements of loss and comprehensive loss, respectively.
	Non-recurring
	The Group measures certain financial assets, including the investments under cost method and equity method on an other than temporary basis, intangible assets, goodwill and fixed assets are marked to fair value when an impairment charge is recognized.
	For the investments under cost and equity method, no impairment was recorded for the year ended December 31, 2012, 2013 and 2014. 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.  No impairment was recorded for the year ended December 31, 2012, 2013 and 2014.
	In accordance with the Group 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 of reporting units annually. The Group concluded that no write down was warranted for years ended December 31, 2012, 2013 and 2014.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Commitments and Contingencies
	15. 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 2017. For the years ended December 31, 2012, 2013 and 2014, lease expense was $6.8 million, $8.8 million and $14.9 million, respectively. Based on the current rental lease agreements, future minimum lease payments required as of December 31, 2014 was as follows:
	Operating lease commitments	Total		Less than One		One to		Three to		More than
				Year		Three Years		Five Years		Five Years
		(In thousands)
	As of December 31, 2014:	$	19,789	$	11,489	$	8,300	$	—	$	—
	Purchase commitments mainly include minimum commitments for internet connection and marketing activities.
	Purchase commitments as of December 31, 2014 was as follows:
	Purchase commitments	Total		Less than One		One to		Three to		More than
				Year		Three Years		Five Years		Five Years
		(In thousands)
	As of December 31, 2014:	$	65,265	$	58,498	$	6,528	$	123	$	116
	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 us, 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.
	There are no claims, lawsuits, investigations or proceedings, including unasserted claims that are probable to be assessed, that have in the recent past had, or to the Group’s knowledge, are reasonably possible to have, a material impact on the Group’s financial position results of operations or cash flow.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events
Subsequent Events
	16. 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_informationcondense

Additional information-condensed financial statements of Weibo Corporation	12 Months Ended
	Dec. 31, 2014
Additional information-condensed financial statements of Weibo Corporation
Additional information-condensed financial statements of Weibo Corporation
	17. 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 combined and consolidated financial statements, except that the Company used the equity method to account for investment in its subsidiaries and VIE.
	The operations of the Company, its subsidiaries and its VIE were included in the combined and 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 and VIE were reported using the equity method of accounting.
	Relevant PRC statutory laws and regulations permit the payment of dividends by the Company’s PRC subsidiary 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 subsidiary 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 combined and 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, 2013 and 2014, 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 combined and consolidated financial statements, if any.
	Condensed Financial Information of Weibo Corporation
	Balance Sheets
	(In thousands, except per share data)
			As of December 31,
			2013			2014
	ASSETS
	Current assets:
	Cash and cash equivalents		$	182,871		$	229,950
	Short-term investments		252,342			166,253
	Prepaid expenses and other current assets		—			229
	Total current assets		435,213			396,432
	Long-term investments		—			13,029
	Investment in subsidiaries and VIE(1)		105,815			160,577
	Total assets		$	541,028		$	570,038
	LIABILITIES, MEZZANINE EQUITY AND SHAREHOLDERS’ DEFICIT
	Accrued liabilities		$	15,650		$	6,543
	Amount due to SINA		259,203			214
	Investor option liability		29,504			—
	Total liabilities		$	304,357		$	6,757
	Commitments and contingencies
	Mezzanine equity
	Convertible preferred shares ($0.00025 of par value per share; 100,000 and nil shares authorized, 30,046 and nil shares issued and outstanding with a redemption value of $16.79 per share and nil as of December 31, 2013 and 2014, respectively)		479,612			—
	Total mezzanine equity (deficit)		479,612			—
	Shareholders’ equity (deficit):
	Shareholders’ equity (deficit):
	Ordinary shares: $0.00025 par value; 600,000 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; 150,392 and 203,658 shares (including 87,649 Class A ordinary shares and 116,009 Class B ordinary shares) issued and outstanding as of December 31, 2013 and 2014, respectively.		$	37		$	51
	Additional paid-in capital		31,352			904,402
	Accumulated other comprehensive income (loss)		521			(2,943		)
	Accumulated deficit		(274,851		)	(338,229		)
	Total shareholders’ equity (deficit)		(242,941		)	563,281
	Total liabilities, mezzanine equity and shareholders’ equity (deficit)		$	541,028		$	570,038
	Condensed Financial Information of Weibo Corporation
	Statements of Loss and Comprehensive Loss
	(In thousands)
			Year Ended December 31,
			2012			2013			2014
	Operating loss		$	(1,841	)	$	(31,764	)	$	(1,086	)
	Interest and other income (expenses), net		(4,923		)	(2,051		)	5,034
	Change in fair value of investor option liability		—			21,064			(46,972		)
	Other loss, net
	Share of loss of subsidiaries and VIE		(95,722		)	(25,364		)	(20,354		)
	Net loss attributable to Weibo		(102,486		)	(38,115		)	(63,378		)
	Other comprehensive income (loss)
	Currency translation adjustments attributable to Weibo		18			(372		)	(1,397		)
	Available-for-sale fair value change		—			—			(2,067		)
	Total comprehensive loss attributable to Weibo		$	(102,468	)	$	(38,487	)	$	(66,842	)
	Condensed Financial Information of Weibo Corporation
	Statements of Cash flow
	(In thousands)
			2012			2013			2014
	Net cash provided by (used in) operating activities		$	(3	)	$	(19,629	)	$	13,152
	Net cash used in investing activities		(117,564		)	(218,908		)	(6,701		)
	Net cash provided by financing activities		108,523			421,370			40,628
	Net increase (decrease) in cash and cash equivalents		$	(9,044	)	$	182,833		$	47,079
	Cash and cash equivalents at the beginning of year		$	9,082		$	38		$	182,871
	Cash and cash equivalents at the end of year		$	38		$	182,871		$	229,950
	Supplemental schedule of non-cash investing and financing activities
Investment in subsidiaries and VIE directly financed by SINA (refund to SINA)*		$	121,083		$	19,346		$	(7,536	)
	-1		The following sets forth the changes in the Company’s investments in its subsidiaries and VIE.
		Investment in subsidiaries and VIE
Balance at December 31, 2012		$	25,361
Additional investment made, net		105,818		*
Share of loss of subsidiaries and VIE		(25,364		)
Balance at December 31, 2013		105,815
Additional investment made, net		75,116		*
Share of loss of subsidiaries and VIE		(20,354		)
Balance at December 31, 2014		$	160,577
*For the year ended December 31, 2013, the additional investment represents the amount that the Company is liable to repay SINA, as SINA funded the operating losses of the Company’s subsidiaries and VIE. SINA also funded certain increases in the net operating assets of the Company’s subsidiaries and VIE, which also increased the investment balance and amount due to SINA. For the year ended December 31, 2014, the additional investment mainly consists of the amount that the Company injected for its subsidiaries and VIE’s registered capital. Refer to Note 3 for further details.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Significant Accounting Policies
Basis of presentation and use of estimates
	Basis of presentation and use of estimates
	The preparation of the Group’s combined and consolidated financial statements is in conformity with US GAAP, which requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from such estimates. The Group believes the basis of combination and consolidation, revenue recognition, fair value accounting, income taxes, goodwill and other long-lived assets, allowances for doubtful accounts, stock-based compensation, and the determination of the estimated useful lives of assets reflect the more significant judgments and estimates used in the preparation of its combined and consolidated financial statements.
Non-controlling interests
	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 are not attributable, directly or indirectly, to the Company as the controlling shareholder. To reflect the economic interest held by non-controlling shareholders, net income (loss) attributable to the non-controlling ordinary shareholders is recorded as non-controlling interests in the Company’s combined and consolidated statements of comprehensive income (loss). Non-controlling interests are classified as a separate line item in the equity section of the Company’s combined and consolidated balance sheets and have been separately disclosed in the Company’s combined and consolidated financial statements to distinguish the interests from that of the Company.
Fair value measurements
	Fair value measurements
	Financial instruments
	All financial assets and liabilities are recognized or disclosed at fair value in the combined and 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 related party Alibaba, accounts receivable due from SINA and other related parties, prepaid expenses and other current assets, accounts payable, amount due to SINA, accrued liabilities due to third parties and employees, accrued liabilities due to related parties and deferred revenues approximates fair value because of their short-term nature. See Note 14 Financial instruments for additional information.
Cash equivalents
	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 stated at cost plus accrued interest.
Long-term investments
	Long-term investments
	Long-term investments are comprised of investments in publicly traded and privately held companies. For long-term investments over which we do 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 used the equity method to account for the investment in Weibo Interactive prior to May 2013, when it had significant influence but did not control Weibo Interactive.
	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 and records reductions in carrying values when necessary. Determination of fair value requires significant judgment in the selection of 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 combined and consolidated statements of loss and comprehensive loss.
	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 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, 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 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 the write-down is accounted for as a realized loss charged to 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.
Business combination
	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 combined and consolidated statements of comprehensive income (loss).
	In a business combination achieved in stages, the Company remeasures its previously held equity interest in the acquiree immediately before obtaining control at its acquisition-date fair value and the re-measurement gain or loss, if any, is recognized in earnings. The determination and allocation of fair values to the identifiable assets acquired, liabilities assumed and noncontrolling interests is based on various assumptions and valuation methodologies requiring considerable judgment from management. The most significant variables in these valuations are discount rates, terminal values, the number of years on which to base the cash flow projections, as well as the assumptions and estimates used to determine the cash inflows and outflows. The Company determines discount rates to be used based on the risk inherent in the related activity’s current business model and industry comparisons. Terminal values are based on the expected life of assets, forecasted life cycle and forecasted cash flows over that period.
Long-lived assets
	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 $16.4 million, $21.3 million and $21.8 million for the years ended December 31, 2012, 2013 and 2014, 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 VIEs. 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. The quantitative impairment test consists of a comparison of the fair value of goodwill with its carrying value. For reporting units directly applying a quantitative assessment, the goodwill impairment test is quantitatively performed by comparing the fair values of those reporting units to their carrying amounts. The Group adopted the option to apply the qualitative approach to assess its goodwill on the relevant reporting units. 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.
Stock-based compensation
	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 service-based 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.
	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.
	Prior to the IPO, the determination of estimated fair value of Weibo required complex and subjective judgments due to their limited financial and operating history, unique business risks and limited public information on companies in China similar to Weibo. The Group, with the assistance of an independent valuation firm, evaluated the use of two generally accepted valuation approaches. The income approach was used if a revenue model had been established, the market approach was used if information from comparable companies had been available, or a weighted blend of these two approaches was used if more than one was applicable, to estimate the enterprise value for purposes of recording stock-based compensation in connection with employee stock options and recording fair value changes for option liability to Alibaba. For the market approach, the Group selected guideline companies that engaged in a similar line of business with similar growth prospects and that were subject to similar financial and business risks. Prior to the IPO, the income approach was applied when the revenue model for Weibo had been established and projections of revenues, costs and expenses, incremental working capital and capital expenditures became available as the business developed. After the IPO, the closing market price of the underlying shares on the last trading date prior to the grant dates is applied in determining the fair value of the options and RSUs granted. Changes in these estimates and assumptions could materially affect the determination of fair value of stock-based compensation.
Allowances for doubtful accounts
	Allowances for doubtful accounts
	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.
Revenue recognition
	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.
	Other revenues
	The Group generates other 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 Company. 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 the third-party developed 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 has determined that the game developers are the primary obligors for the game-related service given that 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. The Group views the game developers to be its customers, and 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. Accordingly, the Group records game-related revenue, net of predetermined revenue sharing with the game developers.
	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 net of the game developer proceeds 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 began to offer 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.
Deferred revenues
	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.
Cost of revenues
	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 tax 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. In November 2011, the Ministry of Finance and the State Administration of Taxation promulgated the Pilot Program for Imposition of Value-Added Tax (“VAT”) to Replace Business Tax (“Pilot Program”). Pursuant to the Pilot Program, a VAT was initially imposed in Shanghai starting from January 1, 2012, to replace the business tax in the transport and shipping industry and some of the modern service industries. Effective September 1, 2012, the Pilot Program was expanded to eight other cities and provinces in China, including Beijing. Beginning from August 1, 2013, the Pilot Program was expanded to all regions in PRC. With the implementation of the Pilot Program, the Group is subject to 6.7% VAT and surcharges and 3% cultural business construction fees for certain parts of its advertising and marketing revenues. Prior to the Pilot Program, the Group was subject to 5.6% business tax and surcharges and 3% cultural business construction fees. The total amount of such taxes on its advertising and marketing revenues for the years ended December 31, 2012, 2013 and 2014 were $4.9 million, $12.5 million and $23.2 million, respectively. For other revenues, the business tax and surcharges were 5.6% before the implementation of the Pilot Program and became 6.7% after switching over to the VAT. The implementation of the Pilot Program has not had a significant impact on the Group’s combined and consolidated statements of loss and comprehensive loss for the years ended December 31, 2013 and 2014.
Advertising expenses
	Advertising expenses
	Advertising expenses consist primarily of costs for the promotion of corporate image and product marketing, part of which were allocated from SINA (see Note 1 Reorganization). The Group expenses all advertising costs as incurred and classifies these costs under sales and marketing expenses. For the years ended December 31, 2012, 2013 and 2014, the advertising expenses were $23.5 million, $33.2 million and $70.9 million, respectively.
Product development expenses
	Product development expenses
	Product development expenses consist primarily of payroll-related expenses and infrastructure cost 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.
Operating leases
	Operating leases
	The Group leases office space under operating lease agreements with initial lease term up to three 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 were 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, 2012, 2013 and 2014, were $1.8 million, $3.2 million and $4.0 million, respectively.
Taxation
	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. Income tax liability is calculated based on a separate return basis as if the Group had filed separate tax returns before the Reorganization.
	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.
Foreign currency
	Foreign currency
	The Group’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 and expenses. Translation gains and losses are recorded in accumulated other comprehensive income or loss as a component of shareholders’ equity (deficit). 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 (expense), net.
	Foreign currency translation adjustments included in the Group’s combined and consolidated loss and comprehensive loss for the years ended December 31, 2012, 2013 and 2014 were gain of less than $0.1 million,  loss of $0.4 million and loss of $1.4 million, respectively. 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.
Preferred Shares
	Preferred Shares
	The preferred shares have been classified as mezzanine equity instead of permanent equity in the Group’s combined and consolidated financial statements as these preferred shares are contingently redeemable upon the occurrence of a conditional event (i.e. a liquidation event), which is not solely within the control of the Company. See Note 3—Investment in Weibo for further details.
Loss per share
	Loss per share
	Loss per share is computed in accordance with ASC 260, Earnings per Share. The two-class method is used for computing earnings per share in the event the Group has net income available for distribution. Under the two-class method, net income is allocated between ordinary shares and participating securities based on dividends declared (or accumulated) and participating rights in undistributed earnings as if all the earnings for the reporting period had been distributed. The Company’s convertible preferred shares are participating securities because they are entitled to receive dividends or distributions on an as converted basis. For the periods presented herein, the computation of basic loss per share using the two-class method is not applicable as the Group is in a net loss position and net loss is not allocated to other participating securities, since these securities are not obligated to share the losses in accordance with the contractual terms.
	Basic net loss 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 loss per share is computed using the weighted average number of ordinary shares and potential ordinary shares outstanding during the period under treasury stock method. Potential ordinary shares include options to purchase ordinary shares, RSUs and preferred shares, unless they were anti-dilutive. The computation of diluted net loss 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 loss per share.
Segment reporting
	Segment reporting
	In accordance with ASC 280, Segment Reporting, the Group’s chief operating decision maker (“CODM”), the Chief Executive Officer, reviews the combined and 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 other 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 segments are presented.
Concentration of risks
	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, 2013 and 2014, the Group had $496.2 million and $447.1 million in cash and bank time deposits (with terms generally up to twelve months) with large domestic banks in China, respectively. 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.
	Accounts receivable, including accounts receivable due from third parties, accounts receivable due from related party Alibaba and accounts receivable due from SINA and other related parties, consist primarily of advertising agencies and direct advertising customers. As of December 31, 2013 and 2014, substantially all accounts receivable were derived from the Group’s China operations. Only Alibaba accounted for over 10% of the Group’s net accounts receivable as of December 31, 2013 and 2014.
	Excluding the advertising and marketing revenues from Alibaba, most of the Group’s advertising and marketing revenues are from agencies. The Group’s top 10 advertising agencies in China contributed to 20% and 14% of the Group’s total revenues for the years ended December 31, 2013 and 2014. No customer accounted for over 10% of the Group’s total revenue for the years ended December 31, 2012. Only Alibaba accounted for over 10% of the total revenue for the years ended December 31, 2013 and 2014.
	Concentration of foreign currency risks. For the years ended December 31, 2012, 2013 and 2014, the majority of the Group’s revenues derived and expenses incurred were in RMB. As of December 31, 2013 and 2014, the Group’s cash, cash equivalents and short-term investments balance denominated in RMB was $62.1 million and $9.0 million, accounting for 12% and 2% of the Group’s total cash, cash equivalents and short-term investments balance. As of December 31, 2013 and 2014, the Group’s aggregated net accounts receivable balance (including accounts receivable due from third parties, accounts receivable due from related party Alibaba and accounts receivable due from SINA and other related parties) denominated in RMB was $47.3 million and $120.1 million, accounting for almost all of its net accounts receivable balance. As of December 31, 2013 and 2014, the Group’s current liabilities balance denominated in RMB was $56.2 million and $104.8 million, accounting for 15% and 93% of its total current liabilities balance. Accordingly, the Group may experience economic losses and negative impacts on earnings and equity (deficit) as a result of exchange rate fluctuations of RMB. Moreover, the Chinese government imposes controls on the convertibility of 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.
Comprehensive loss
	Comprehensive loss
	Comprehensive loss is defined as the change in equity of a company during a period from transactions and other events and circumstances excluding transactions resulting from investments from owners and distributions to owners. Comprehensive loss for the periods presented includes net loss and foreign currency translation adjustments.
Recent accounting pronouncements
	Recent accounting pronouncements
	The FASB issued Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, which changes the threshold for reporting discontinued operations and adds new disclosures. The new guidance defines a discontinued operation as a disposal that “represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results.” The standard is required to be adopted by public business entities in annual periods beginning on or after December 15, 2014, and interim periods within those annual periods. Entities may “early adopt” the guidance for new disposals. The Group is in the process of evaluating the impact of adoption of this guidance on the combined and combined and consolidated financial statements.
	In May 2014, the 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 core principle of the guidance is that an entity should recognize revenues to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve that core principle, an entity should apply the following steps:
		·	Step 1: Identify the contract(s) with a customer.
		·	Step 2: Identify the performance obligations in the contract.
		·	Step 3: Determine the transaction price.
		·	Step 4: Allocate the transaction price to the performance obligations in the contract.
		·	Step 5: Recognize revenue when (or as) the entity satisfies a performance obligation.
	For a public entity, the amendments in this ASU are effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. In April 2015, the FASB proposed a one-year delay in the effective date and companies will be allowed to early adopt as of the original effective date..  The Group is in the process of evaluating the impact of adoption of this guidance on the combined and consolidated financial statements.
	In June 2014, the FASB issued a new pronouncement which requires that a performance target that affects vesting and that could be achieved after the requisite service period is treated as a performance condition. A reporting entity should apply existing guidance in Topic 718, Compensation—Stock Compensation, as it relates to awards with performance conditions that affect vesting to account for such awards. The performance target should not be reflected in estimating the grant-date fair value of the award. Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered. If the performance target becomes probable of being achieved before the end of the requisite service period, the remaining unrecognized compensation cost should be recognized prospectively over the remaining requisite service period. The total amount of compensation cost recognized during and after the requisite service period should reflect the number of awards that are expected to vest and should be adjusted to reflect those awards that ultimately vest. The requisite service period ends when the employee can cease rendering service and still be eligible to vest in the award if the performance target is achieved. The amendments in this ASU are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted. The Group does not expect the adoption of this guidance will have a significant effect on its financial position, results of operations, or cash flows.
	In August 2014, the FASB issued a new pronouncement Presentation of Financial Statements — Going Concern. This standard requires management to evaluate for each annual and interim reporting period whether it is probable that the reporting entity will not be able to meet its obligations as they become due within one year after the date that the financial statements are issued. If the entity is in such a position, the standard provides for certain disclosures depending on whether or not the entity will be able to successfully mitigate its going concern status. This guidance is effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016. Early application is permitted. The Group does not expect the adoption of this guidance will have a significant effect on its financial position, results of operations, or cash flows.
	In February 2015, the FASB issued ASU 2015-02, “Consolidation (Topic 810) - Amendments to the Consolidation Analysis”, which provides guidance for reporting entities that are required to evaluate whether they should consolidate certain legal entities. In accordance with ASU 2015-02, all legal entities are subject to reevaluation under the revised consolidation model. ASU 2015-02 is effective for public business entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early adoption is permitted. The Group is currently evaluating the impact on the adoption of ASU 2015-02 to its combined and consolidated financial statements.

Operations_and_reorganization_

Operations and reorganization (Tables)	12 Months Ended
	Dec. 31, 2014
Operations and reorganization
Schedule of ownership structure of the subsidiaries, VIE and VIE's subsidiary
	Company	Date of		Place of		Percentage of
		Incorporation		Incorporation		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 its subsidiary**
	Beijing Weimeng Technology Co., Ltd (“Weimeng” or the VIE)	August 9, 2010		PRC		100	%
	Beijing Weibo Interactive Internet Technology Co., Ltd. (‘‘Weibo Interactive’’)	Acquired in May 2013 (Note 5)		PRC		100	%
Schedule of allocated expenses from SINA
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Cost of revenues	$	17,769		$	14,760		$	4
	Sales and marketing	2,506			6,074			17,417
	Product development	21,111			19,256			18,362
	General and administrative	2,574			4,215			6,581
		$	43,960		$	44,305		$	42,360
Schedule of assets, liabilities, results of operations and cash flows of the VIE and its subsidiary taken as a whole, including the Predecessor Operations
		As of December 31,
		2013			2014
		(In thousands)
	Cash, Cash Equivalents and Short-term Investments	$	9,200		$	9,271
	Accounts receivable	46,575			118,891
	Property and equipment, net	1,155			2,092
	Goodwill	7,517			11,357
	Intangible assets	3,071			3,538
	Long-term Investments	—			19,016
	Others	6,042			10,223
	Total assets	$	73,560		$	174,388
	Accrued liabilities	$	18,180		$	34,324
	Amount due to SINA	38,620			1,514
	Amount due to the subsidiaries of the Group	20,933			121,977
	Deferred revenues	8,901			14,117
	Others	768			1,174
	Total liabilities	$	87,402		$	173,106
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Net revenues	$	54,432		$	169,819		$	298,767
	Net income (loss)	$	4,531		$	24,864		$	(4,404	)
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Net cash provided by (used in) operating activities	$	(5,564	)	$	25,236		$	9,298
	Net cash used in investing activities	$	—		$	(3,120	)	$	(2,424	)
	Net cash provided by (used in) financing activities	$	5,862		$	(14,498	)	$	(6,965	)
	Net increase (decrease) in cash and cash equivalents	$	298		$	7,618		$	(91	)

Investment_in_Weibo_Tables

Investment in Weibo (Tables)	12 Months Ended
	Dec. 31, 2014
Investment in Weibo
Schedule of preference shares
	Issuance Date	Shares outstanding	Carrying Amount
			(In thousands)
	April 29, 2013	30,046,154	$	479,612

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents and Short-term Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Cash, Cash Equivalents and Short-term Investments
Schedule of Cash, cash equivalents and short-term investments
		As of December 31,
		2013		2014
		(In thousands)
	Cash and cash equivalents:
	Cash	$	13,332	$	53,512
	Cash equivalents:
	Bank time deposits	233,104		229,950
		246,436		283,462
	Short-term investments:
	Bank time deposits	252,342		166,414
	Total cash, cash equivalents and short-term investments	$	498,778	$	449,876

Longterm_Investments_and_Acqui

Long-term Investments and Acquisition (Tables)	12 Months Ended
	Dec. 31, 2014
Schedule of changes in long-term investments
		Cost Method			Equity Method			Available-for-Sale			Total
								Securities
		(In thousands)
	Balance at January 1, 2012	$	—		$	4,905		$	—		$	4,905
	Loss from long-term investments	—			(1,340		)	—			(1,340		)
	Balance at December 31, 2012	$	—		$	3,565		$	—		$	3,565
	Loss from long-term investments	—			(1,236		)	—			(1,236		)
	Investments made	5,500			4,635			—			10,135
	Remeasurement gain upon obtaining control	—			3,116			—			3,116
	Transfer from long-term investments to a wholly owned subsidiary	—			(10,080		)	—			(10,080		)
	Balance at December 31, 2013	$	5,500		$	—		$	—		$	5,500
	Investments made	26,670			—			15,096			41,766
	Unrealized loss	—			—			(2,067		)	(2,067		)
	Balance at December 31, 2014	$	32,170		$	—		$	13,029		$	45,199
Schedule of changes in goodwill by segment
		Advertising &			Other			Total
		Marketing
		(In thousands)
	Balance as of January 1, 2013	$	—		$	—		$	—
	Acquisition of Weibo Interactive	—			7,517			7,517
	Balance as of December 31, 2013	$	—		$	7,517		$	7,517
	Acquisition of game developer	—			3,840			3,840
	Others	—			295			295
	Balance as of December 31, 2014	$	—		$	11,652		$	11,652
Schedule of estimated amortization expenses
	As of December 31, 2014, estimated amortization expenses for future periods are expected to be as follows:
	Year Ended December 31,	(In thousands)
	2015	$	1,498
	2016	769
	2017	688
	2018	584
	2019 and thereafter	—
	Total expected amortization expense	$	3,539
Weibo Interactive
Schedule of fair value of the assets acquired and the liabilities assumed
		As of acquisition date
		(In thousands)
	Cash consideration for the remaining 45% equity interest	$	4,635
	Fair value of previously held 55% equity interest	5,445
	Total consideration	10,080
	Tangible assets	98
	Identifiable intangible assets acquired	3,560
	Liabilities assumed	(1,095		)
	Goodwill	7,517
	Total consideration	$	10,080
Gametree
Schedule of fair value of the assets acquired and the liabilities assumed
		As of acquisition date
		(In thousands)
	Cash consideration	$	3,062
	Non-controlling interests	292
	Total consideration	3,354
	Tangible assets	1,518
	Identifiable intangible assets acquired	1,688
	Liabilities assumed	(3,692		)
	Goodwill	3,840
	Total consideration	$	3,354

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation
Schedule of stock-based compensation
		Year Ended December 31,
		2012			2013			2014
		(In thousands)
	Cost of revenues	$	201		$	4,253		$	755
	Sales and marketing	330			6,150			1,583
	Product development	638			9,209			4,392
	General and administrative	668			11,630			7,049
		$	1,837		$	31,242		$	13,779
Schedule of assumptions used to value the option grants
		Year Ended December 31,
		2012		2013		2014*
	Stock options:
	Expected term (in years)	3.5 - 4.8		3.5 - 4.8		N/A
	Expected volatility	60% - 63%		54% -61%		N/A
	Risk-free interest rate	0.4% - 0.8%		0.5% - 1.2%		N/A
	Expected dividend yield	—		—		—
	* No stock options were granted in 2014.
Summary of the number of shares available for issuance
		Shares Available
		(In thousands)
	December 31, 2011	6,728
	Granted	(2,175	)
	Cancelled/expired/forfeited	908
	Repurchased	2,625
	December 31, 2012	8,086
	Granted*	(4,772	)
	Cancelled/expired/forfeited	1,157
	Repurchased	177
	December 31, 2013	4,648
	Addition (2014 plan)	1,000
	Granted*	(2,951	)
	Cancelled/expired/forfeited	41
	December 31, 2014	2,738
	*In 2013, 0.8 million restricted share units, equivalent to 1.4 million option shares, and 3.4 million stock options were granted under the 2010 plan. In 2014,  3.0 million restricted share units and no stock option were granted under the 2014 plan.
Summary of option activities under the Company' stock option program
		Options		Weighted Average			Weighted Average		Aggregate
		Outstanding		Exercise Price			Remaining		Intrinsic Value
							Contractual Life
		(In thousands)					(In years)		(In thousands)
	December 31, 2011	28,272		$	0.41		5.5		$	82,726
	Granted	2,175		$	3.34
	Exercise	(3,445	)	$	0.36
	Cancelled/expired/forfeited	(908	)	$	0.6
	Repurchased	(2,625	)	$	0.36
	December 31, 2012	23,469		$	0.69		4.6		$	60,226
	Granted	3,372		$	3.38
	Exercise	(3,449	)	$	0.38
	Cancelled/expired/forfeited	(1,157	)	$	2.49
	Repurchased	(3,674	)	$	0.45
	December 31, 2013	18,561		$	1.17		4.3		$	239,975
	Granted	—		$	—
	Exercise	(3,697	)	$	0.52
	Cancelled/expired/forfeited	(534	)	$	2.84
	Repurchased	—		$	—
	December 31, 2014	14,330		$	1.28		3.2		$	185,684
	Vested and expected to vest as of December 31, 2013	18,261		$	1.14		4.3		$	236,716
	Exercisable as of December 31, 2013	8,957		$	0.48		3.7		$	122,026
	Vested and expected to vest as of December 31, 2014	14,261		$	1.27		3.2		$	184,937
	Exercisable as of December 31, 2014	11,446		$	0.76		2.7		$	154,235
Schedule of stock options outstanding
	Range of Exercise Prices	Options		Weighted			Options		Weighted		Weighted Average
		Outstanding		Average			Exercisable		Average		Remaining
				Exercise Price					Exercise Price		Contractual Life
		(In thousands)					(In thousands)				(In years)
	As of December 31, 2013
	$0.36 - 0.41	12,571		$	0.36		7,989		$	0.36	3.7
	$0.96 - 1.80	1,324		$	1.14		830		$	1.14	4.3
	$3.25 - $3.36	2,822		$	3.30		138		$	3.26	5.6
	$3.43 - $3.50	1,844		$	3.48		—		$	—	6.6
		18,561		$	1.17		8,957		$	0.48	4.3
	As of December 31, 2014
	$0.36 - 0.41	9,337		$	0.37		9,337		$	0.37	2.3
	$0.96 - 1.80	844		$	1.19		764		$	1.18	3.1
	$3.25 - $3.36	2,542		$	3.29		1,345		$	3.30	4.8
	$3.43 - $3.50	1,607		$	3.48		—		$	—	5.5
		14,330		$	1.28		11,446		$	0.76	3.2
Summary of service-based restricted share unit activities
		Shares		Weighted-Average
		Granted		Grant Date
				Fair Value
		(In
		thousands)
	December 31, 2013	800		$	13.19
	Awarded	2,951		$	17.11
	Vested	(203	)	$	13.19
	Cancelled	(41	)	$	17.23
	December 31, 2014	3,507		$	16.44

Other_Balance_Sheet_Components1

Other Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2014
Other Balance Sheet Components
Schedule of other balance sheet components
		As of December 31,
		2012		2013			2014
				(In thousands)
	Accounts receivable, net:
	Due from third parties			$	27,189		$	39,277
	Due from SINA and other related parties			2,058			18,648
	Due from related party Alibaba			21,299			64,725
	Total gross amount			$	50,546		$	122,650
	Allowance for doubtful accounts:
	Balance at the beginning of the year	—		(897		)	(3,242		)
	Additional provision charged to expenses	(897	)	(2,345		)	(2,138		)
	Write-off	—		—			2,940
	Balance at the end of the year	(897	)	(3,242		)	(2,440		)
				$	47,304		$	120,210
	Prepaid expenses and other current assets:
	Rental and other deposits			$	3,244		$	3,319
	Current deferred tax assets			744			18
	Input VAT			—			1,526
	Prepayment for long-term investments			495			1,942
	Advertising prepayment			—			3,936
	Prepayment to outsource service providers			—			1,730
	Prepayment for license fee			—			1,872
	Others			1,210			1,761
				$	5,693		$	16,104
	Property and equipment, net:
	Computers and equipment			$	74,843		$	89,069
	Leasehold improvements			4,340			4,944
	Furniture and fixtures			1,490			2,052
	Others			392			730
				81,065			96,795
	Less: Accumulated depreciation			(45,363		)	(65,921		)
				$	35,702		$	30,874
	Accrued liabilities*:
	Payroll and welfare			$	7,336		$	19,686
	Amounts owed on option/share repurchase			12,073			1,203
	Content fees (including amounts due to related parties of $486 and nil as of December 31, 2013 and 2014)			572			1,005
	Marketing expenses (including amounts due to related parties of $3,021 and 5,786 as of December 31, 2013 and 2014)			11,288			19,806
	Internet connection costs			1,591			6,834
	Employee payroll withholding taxes			3,950			3,547
	Sales rebates			7,007			14,126
	Advertisement production costs			2,774			—
	Professional fees			912			3,138
	Revenue share			3,097			3,057
	VAT and other tax payable			702			6,629
	Payable to other service providers			1,800			1,074
	Payable to outsourced service providers			671			1,375
	Others			2,641			5,998
				$	56,414		$	87,478
	* Include amounts due to third parties, employees and related parties.

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes
Schedule of components of loss before income taxes
		Year Ended December 31,
		2012			2013			2014
		(In thousands, except percentage)
	Loss before income tax expenses	$	(104,037	)	$	(37,844	)	$	(61,506	)
	Loss from non-China operations	$	(2,950	)	$	(13,341	)	$	(54,073	)
	Loss from China operations	$	(101,087	)	$	(24,503	)	$	(7,433	)
	Income tax expenses (benefits) applicable to China operations	$	(1,551	)	$	271		$	1,128
	Effective tax rate for China operations	1.5		%	(1.1		)%	(15.2		)%
Schedule of current and deferred portion of income tax expenses (benefits)
		Years Ended December 31,
		2012			2013			2014
		(In thousands)
	Deferred tax expenses (benefits)	$	(1,551	)	$	271		$	866
	Current income tax expenses	—			—			262
	Income tax expenses (benefits)	$	(1,551	)	$	271		$	1,128
Schedule of reconciliation between the statutory EIT rate and the effective tax rate
		Year Ended December 31,
		2012		2013		2014
	Statutory EIT rate	(25.0	)%	(25.0	)%	(25.0	)%
	Permanent differences	3.2	%	0.6	%	3.0	%
	Change in valuation allowance	23.3	%	23.3	%	6.8	%
	Effective tax rate for China operations	1.5	%	(1.1	)%	(15.2	)%
Schedule of deferred tax assets and liabilities
		As of December 31,
		2013			2014
		(In thousands)
	Deferred tax assets:
	Net operating loss carry forwards	$	49,800		$	42,096
	Less: valuation allowance	(48,577		)	(42,065		)
	Net deferred tax assets	$	1,223		$	31
	Including-Current deferred tax assets	744			18
	-Non-current deferred tax assets	479			13
	Deferred tax liabilities:
	Acquired intangible assets	$	768		$	873
	Total deferred tax liabilities	$	768		$	873

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2014
Related Party Transactions
Schedule of significant related party transactions
	Company Name		Relationship with the Company
	SINA		Parent and affiliates under common control.
	Alibaba		Strategic partner and significant shareholder of the Company (Post April 29, 2013).
	Weibo Interactive		Investee accounted for under the equity method until May 2013 and wholly owned under common control thereafter.
			Year Ended December 31,
			2012		2013		2014
			(In thousands)
	Transactions with SINA
	Deemed contribution from SINA(1)		$	—	$	13,092	$	61,176
	Legal transfer of Weibo Interactive and recognition of due to SINA(2)		$	—	$	10,080	$	—
	Costs and expenses allocated from SINA(3)		$	43,960	$	44,305	$	42,360
	Interest expense on amount due to SINA		$	4,923	$	6,709	$	2,838
	Repayment of amount due to SINA(4)		$	—	$	159,816	$	276,614
		-1		The $13.1 million in deemed contribution from SINA for the year ended December 31, 2013 included $4.6 million related to the step-up acquisition of Weibo Interactive in May 2013 and $8.5 million in interest expensed waived (Note 1). The $61.2 million in deemed contribution from SINA for the year ended December 31, 2014 represents the discount borne by SINA upon the settlement of investor options (Note 3).
		-2		In connection with the Reorganization, SINA transferred 100% equity interest in Weibo Interactive to the Group in December 2013 for a consideration of $10.1 million (Note 1).
		-3		Costs and expenses allocated from SINA represent the charge for certain services provided by SINA’s affiliates and charged to the Company using actual cost allocation based on proportional utilization (Note 1). In addition to the allocated costs and expenses, SINA also billed $15.1 million for other costs and expenses associated with Weibo business.
		-4		For the year ended December 31, 2014, the Company repaid approximately $276.6 million for the loan and relevant interests to SINA (Note 3).
			Year Ended December 31,
			2012		2013		2014
			(In thousands)
	Transactions with Alibaba
	Advertising and marketing services provided to Alibaba		$	—	$	49,135	$	107,587
	Deemed contribution from Alibaba(5)		$	—	$	—	$	15,300
		-5		The $15.3 million for the year ended December 31, 2014, represents the discount borne by Alibaba upon the settlement of investor options (Note 3).
Schedule of outstanding balance due to or from related parties
			As of December 31,
			2013		2014
			(In thousands)
	Amount due to SINA		$	267,722	$	1,717
	Accounts receivable due from SINA(6)		$	1,830	$	3,151
	Accounts receivable due from Alibaba		$	21,299	$	64,725
	Accrued liabilities due to SINA(6)		$	3,507	$	—
		-6		The Group settles customer and supplier balances with SINA when the third-parties settle such amount with SINA. Any uncollectible losses arising from the accounts receivable due from SINA are passed on to the Group.

Loss_Per_Share_Tables

Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Loss Per Share
Schedule of basic and diluted net loss per share
		Year Ended December 31,
		2012			2013			2014
		(In thousands, except per share data)
	Basic net loss per share calculation:
	Numerator:
	Net loss attributable to ordinary shareholders	$	(102,486	)	$	(38,115	)	$	(63,378	)
	Denominator:
	Weighted average ordinary shares outstanding	140,831			146,820			186,878
	Basic net loss per share attributable to ordinary shareholders	$	(0.73	)	$	(0.26	)	$	(0.34	)
	Diluted net loss per share calculation:
	Numerator:
	Net loss attributable for calculating diluted net loss per share	$	(102,486	)	$	(38,115	)	$	(63,378	)
	Denominator:
	Weighted average ordinary shares outstanding	140,831			146,820			186,878
	Weighted average ordinary shares equivalents:
	Shares used in computing diluted net loss per share attributable to ordinary shareholders	140,831			146,820			186,878
	Diluted net loss per share attributable to ordinary shareholders	$	(0.73	)	$	(0.26	)	$	(0.34	)

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Information
Summary of revenues
	Revenues	Advertising & Marketing		Other		Total
		(In thousand)
	Year ended December 31, 2012	$	51,049	$	14,880	$	65,929
	Year ended December 31, 2013	$	148,426	$	39,887	$	188,313
	Year ended December 31, 2014	$	264,782	$	69,390	$	334,172

Financial_Instruments_Tables

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
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		Significant Other		Significant
					Active Market		Observable Inputs		Unobservable Inputs
					for Identical Assets		(Level 2)		(Level 3)
					(Level 1)
	As of December 31, 2013:
	Bank time deposits*	$	485,446		$	—	$	485,446	$	—
	Investor option liability	(29,504		)	—		—		(29,504		)
	Total	$	455,942		$	—	$	485,446	$	(29,504	)
	As of December 31, 2014:
	Bank time deposits*	$	396,364		$	—	$	396,364	$	—
	Available-for-sale securities**	13,029			13,029		—		—
	Total	$	409,393		$	13,029	$	396,364	$	—
	*Included in cash and cash equivalents and short-term investments on the Group’s combined and consolidated balance sheets.
	** Included in long-term investments.
Schedule of key inputs used in investor option liability valuation
		As of
		December 31, 2013
	Expected dividend yield	—
	Risk-free interest rate	0.30		%
	Expected volatility	53		%
	Expected life (in years)	1.40
	Fair value per ordinary share	$	14.10

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Schedule of future minimum rental payments
	Operating lease commitments	Total		Less than One		One to		Three to		More than
				Year		Three Years		Five Years		Five Years
		(In thousands)
	As of December 31, 2014:	$	19,789	$	11,489	$	8,300	$	—	$	—
Schedule of purchase commitments
	Purchase commitments	Total		Less than One		One to		Three to		More than
				Year		Three Years		Five Years		Five Years
		(In thousands)
	As of December 31, 2014:	$	65,265	$	58,498	$	6,528	$	123	$	116

Additional_informationcondense1

Additional information-condensed financial statements of Weibo Corporation (Tables)	12 Months Ended
	Dec. 31, 2014
Balance sheets
Balance Sheets
	Condensed Financial Information of Weibo Corporation
	Balance Sheets
	(In thousands, except per share data)
		As of December 31,
		2013			2014
	ASSETS
	Current assets:
	Cash and cash equivalents	$	182,871		$	229,950
	Short-term investments	252,342			166,253
	Prepaid expenses and other current assets	—			229
	Total current assets	435,213			396,432
	Long-term investments	—			13,029
	Investment in subsidiaries and VIE(1)	105,815			160,577
	Total assets	$	541,028		$	570,038
	LIABILITIES, MEZZANINE EQUITY AND SHAREHOLDERS’ DEFICIT
	Accrued liabilities	$	15,650		$	6,543
	Amount due to SINA	259,203			214
	Investor option liability	29,504			—
	Total liabilities	$	304,357		$	6,757
	Commitments and contingencies
	Mezzanine equity
	Convertible preferred shares ($0.00025 of par value per share; 100,000 and nil shares authorized, 30,046 and nil shares issued and outstanding with a redemption value of $16.79 per share and nil as of December 31, 2013 and 2014, respectively)	479,612			—
	Total mezzanine equity (deficit)	479,612			—
	Shareholders’ equity (deficit):
	Shareholders’ equity (deficit):
	Ordinary shares: $0.00025 par value; 600,000 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; 150,392 and 203,658 shares (including 87,649 Class A ordinary shares and 116,009 Class B ordinary shares) issued and outstanding as of December 31, 2013 and 2014, respectively.	$	37		$	51
	Additional paid-in capital	31,352			904,402
	Accumulated other comprehensive income (loss)	521			(2,943		)
	Accumulated deficit	(274,851		)	(338,229		)
	Total shareholders’ equity (deficit)	(242,941		)	563,281
	Total liabilities, mezzanine equity and shareholders’ equity (deficit)	$	541,028		$	570,038
Statements of Loss and Comprehensive Loss
	Condensed Financial Information of Weibo Corporation
	Statements of Loss and Comprehensive Loss
	(In thousands)
		Year Ended December 31,
		2012			2013			2014
	Operating loss	$	(1,841	)	$	(31,764	)	$	(1,086	)
	Interest and other income (expenses), net	(4,923		)	(2,051		)	5,034
	Change in fair value of investor option liability	—			21,064			(46,972		)
	Other loss, net
	Share of loss of subsidiaries and VIE	(95,722		)	(25,364		)	(20,354		)
	Net loss attributable to Weibo	(102,486		)	(38,115		)	(63,378		)
	Other comprehensive income (loss)
	Currency translation adjustments attributable to Weibo	18			(372		)	(1,397		)
	Available-for-sale fair value change	—			—			(2,067		)
	Total comprehensive loss attributable to Weibo	$	(102,468	)	$	(38,487	)	$	(66,842	)
Statements of Cash flow
	Condensed Financial Information of Weibo Corporation
	Statements of Cash flow
	(In thousands)
		2012			2013			2014
	Net cash provided by (used in) operating activities	$	(3	)	$	(19,629	)	$	13,152
	Net cash used in investing activities	(117,564		)	(218,908		)	(6,701		)
	Net cash provided by financing activities	108,523			421,370			40,628
	Net increase (decrease) in cash and cash equivalents	$	(9,044	)	$	182,833		$	47,079
	Cash and cash equivalents at the beginning of year	$	9,082		$	38		$	182,871
	Cash and cash equivalents at the end of year	$	38		$	182,871		$	229,950
	Supplemental schedule of non-cash investing and financing activities
	Investment in subsidiaries and VIE directly financed by SINA (refund to SINA)*	$	121,083		$	19,346		$	(7,536	)
Weibo Corporation
Balance sheets
Schedule of changes in the company's investments in its subsidiaries and VIE
		Investment in subsidiaries and VIE
	Balance at December 31, 2012	$	25,361
	Additional investment made, net	105,818		*
	Share of loss of subsidiaries and VIE	(25,364		)
	Balance at December 31, 2013	105,815
	Additional investment made, net	75,116		*
	Share of loss of subsidiaries and VIE	(20,354		)
	Balance at December 31, 2014	$	160,577
	*For the year ended December 31, 2013, the additional investment represents the amount that the Company is liable to repay SINA, as SINA funded the operating losses of the Company’s subsidiaries and VIE. SINA also funded certain increases in the net operating assets of the Company’s subsidiaries and VIE, which also increased the investment balance and amount due to SINA. For the year ended December 31, 2014, the additional investment mainly consists of the amount that the Company injected for its subsidiaries and VIE’s registered capital. Refer to Note 3 for further details.

Operations_and_reorganization_1

Operations and reorganization (Details) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-13	Apr. 29, 2013	Dec. 31, 2013	Apr. 17, 2014	Apr. 30, 2014	Dec. 31, 2011
Operations and reorganization
Proceeds from IPO	$306,491,000
Number of Class A shares converted from Class B shares	1
Interest expense	2,838,000	6,709,000	4,923,000
Amount due to SINA	1,717,000	267,722,000				267,722,000
SINA
Operations and reorganization
Interest expense	2,838,000	6,709,000	4,923,000
Interest waived		8,500,000
Amount due to SINA	1,717,000	267,722,000				267,722,000
SINA | Weibo Interactive
Operations and reorganization
Cash consideration for remaining equity interest				4,600,000
SINA | Amount due to SINA
Operations and reorganization
Interest rate, minimum	2.55%
Interest rate, maximum	3.05%
Interest expense	2,800,000	6,700,000	4,900,000
Interest waived					8,500,000
Amount due to SINA	1,700,000	267,700,000			250,000,000	267,700,000
Interest payable		4,800,000				4,800,000
SINA | Transfer of Equity Interest in Weibo Interactive
Operations and reorganization
Percentage of equity interest transferred to Group						100.00%
Consideration for transfer of equity interest						10,100,000
Alibaba | SINA
Operations and reorganization
Number of ordinary shares acquired by investor							23,990,778
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	1
Class A ordinary shares | Alibaba
Operations and reorganization
Issuance of shares (in shares)					4,800,000
Number of ordinary shares acquired by investor							29,990,778
Class A ordinary shares | Alibaba | SINA
Operations and reorganization
Number of ordinary shares acquired by investor							21,067,300
Class B ordinary shares
Operations and reorganization
Number of votes each share is entitled to	3
IPO | Class A ordinary shares
Operations and reorganization
Issuance of shares (in shares)								19,320,000
Proceeds from IPO								306,500,000
IPO | Class A ordinary shares | Alibaba
Operations and reorganization
Number of ordinary shares acquired by investor							6,000,000
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 | Weibo Interactive
Operations and reorganization
Equity interest percentage acquired by parent and accounted for under the equity method of accounting									55.00%
Remaining equity interest acquired (as a percent)				45.00%
Cash consideration for remaining equity interest				$4,635,000

Operations_and_reorganization_2

Operations and reorganization (Details 2) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2011
Operations and reorganization
Allocated expenses from SINA	$42,360,000	$44,305,000	$43,960,000
Interest-free loans to the VIE's shareholders	10,500,000	1,500,000		1,500,000
Aggregate accumulated losses	18,000,000	13,600,000
Assets and liabilities of the VIEs and their subsidiaries
Cash, Cash Equivalents and Short-term Investments	449,876,000	498,778,000		498,778,000
Property and equipment, net	30,874,000	35,702,000		35,702,000
Goodwill	11,652,000	7,517,000		7,517,000
Intangible assets	3,539,000	3,071,000		3,071,000
Long-term Investments	45,199,000	5,500,000	3,565,000	5,500,000	4,905,000
Others	327,000	3,369,000		3,369,000
Accrued liabilities	87,478,000	56,414,000		56,414,000
Amount due to SINA	1,717,000	267,722,000		267,722,000
Deferred revenues	20,957,000	15,031,000		15,031,000
Results of operations of the VIEs and their subsidiaries
Net revenues	334,172,000	188,313,000	65,929,000
Net income (loss)	-63,378,000	-38,115,000	-102,486,000
Cash flows of the VIE and its subsidiary
Net cash provided by (used in) operating activities	-24,679,000	-9,369,000	-103,642,000
Net cash used in investing activities	21,045,000	-153,365,000	-136,526,000
Net cash provided by (used in) financing activities	42,695,000	406,753,000	229,368,000
Assets, except for registered capital of VIEs, that can only be used to settle obligations of the respective VIEs	0	0		0
Registered capital of VIE and its subsidiary	15,700,000	7,000,000		7,000,000
Term of loan agreements	10 years
Service fees revenue charged to VIE	187,800,000	79,200,000	0
Term of trademark license agreements	1 year
SINA
Operations and reorganization
Allocated expenses from SINA	42,360,000	44,305,000	43,960,000
Assets and liabilities of the VIEs and their subsidiaries
Amount due to SINA	1,717,000	267,722,000		267,722,000
SINA | Transfer of Equity Interest in Weibo Interactive
Cash flows of the VIE and its subsidiary
Consideration for transfer of equity interest to Group				10,100,000
Consolidated VIEs
Operations and reorganization
Allocated expenses from SINA	16,100,000	37,200,000	42,700,000
Assets and liabilities of the VIEs and their subsidiaries
Cash, Cash Equivalents and Short-term Investments	9,271,000	9,200,000		9,200,000
Accounts receivable	118,891,000	46,575,000		46,575,000
Property and equipment, net	2,092,000	1,155,000		1,155,000
Goodwill	11,357,000	7,517,000		7,517,000
Intangible assets	3,538,000	3,071,000		3,071,000
Long-term Investments	19,016,000
Others	10,223,000	6,042,000		6,042,000
Total assets	174,388,000	73,560,000		73,560,000
Accrued liabilities	34,324,000	18,180,000		18,180,000
Amount due to SINA	1,514,000	38,620,000		38,620,000
Amount due to the subsidiaries of the Group	121,977,000	20,933,000		20,933,000
Deferred revenues	14,117,000	8,901,000		8,901,000
Others	1,174,000	768,000		768,000
Total liabilities	173,106,000	87,402,000		87,402,000
Results of operations of the VIEs and their subsidiaries
Net revenues	298,767,000	169,819,000	54,432,000
Net income (loss)	-4,404,000	24,864,000	4,531,000
Cash flows of the VIE and its subsidiary
Net cash provided by (used in) operating activities	9,298,000	25,236,000	-5,564,000
Net cash used in investing activities	-2,424,000	-3,120,000
Net cash provided by (used in) financing activities	-6,965,000	-14,498,000	5,862,000
Net increase (decrease) in cash and cash equivalents	-91,000	7,618,000	298,000
Amount of advertising and marketing service provided by the VIE to the related party	136,600,000	49,100,000	0
Amount of game platform maintenance services provided by a related party	0	0	3,500,000
Costs of revenues
Operations and reorganization
Allocated expenses from SINA		14,760,000	17,769,000
Sales and marketing
Operations and reorganization
Allocated expenses from SINA	17,417,000	6,074,000	2,506,000
Product development
Operations and reorganization
Allocated expenses from SINA	18,362,000	19,256,000	21,111,000
General and administrative
Operations and reorganization
Allocated expenses from SINA	$6,581,000	$4,215,000	$2,574,000

Significant_Accounting_Policie2

Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and equipment
Depreciation	$21.80	$21.30	$16.40
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
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_Policie3

Significant Accounting Policies (Details 2) (USD $)	0 Months Ended	12 Months Ended			8 Months Ended
	Sep. 01, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2012
	item	segment
Game-related service
Maximum period for recognition of revenues after purchase of in-game credits		1 month
Data licensing arrangement term		1 year
Cost of revenues
Number of other cities and provinces in China to which the Pilot Program was expanded	8
Advertising expense
Advertising expenses		$70,900,000	$33,200,000	$23,500,000
Operating leases
Maximum initial lease term of office space		3 years
Allocated rental expenses from SINA		42,360,000	44,305,000	43,960,000
Foreign currency
Foreign currency translation adjustments		-1,401,000	-372,000	18,000
Segment reporting
Number of principal business segments		2
Stock options
Stock-based compensation
Vesting period of stock options granted		4 years
Service-based restricted share units
Stock-based compensation
Vesting period of stock options granted		4 years
Rental expense
Operating leases
Allocated rental expenses from SINA		4,000,000	3,200,000	1,800,000
Advertising and marketing revenues
Cost of revenues
VAT and surcharges (as a percent)		6.70%
Cultural business construction fees (as a percent)		3.00%			3.00%
Business tax and surcharges (as a percent)					5.60%
Taxes on advertising and marketing revenues		$23,200,000	$12,500,000	$4,900,000
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
Other revenues
Cost of revenues
VAT and surcharges (as a percent)		6.70%
Business tax and surcharges (as a percent)					5.60%

Significant_Accounting_Policie4

Significant Accounting Policies (Details 3) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Concentration of risks
Cash, cash equivalents and short-term investments	$449,876	$498,778
Current liabilities denominated in RMB	112,572	369,495
Cash, cash equivalents and short-term investments | Concentration of credit risk | China
Concentration of risks
Cash, cash equivalents and short-term investments	447,100	496,200
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	9,000	62,100
Percentage of benchmark derived from specified source	2.00%	12.00%
Consolidated net revenues benchmark | Customer concentration risk | Alibaba | Minimum
Concentration of risks
Percentage of benchmark derived from specified source	10.00%	10.00%
Consolidated net accounts receivables benchmark | Concentration of credit risk | Alibaba | Minimum
Concentration of risks
Percentage of benchmark derived from specified source	10.00%	10.00%
Consolidated net accounts receivables benchmark | Concentration of foreign currency risks | RMB
Concentration of risks
Accounts receivable denominated in RMB	120,100	47,300
Current liabilities | Concentration of foreign currency risks | RMB
Concentration of risks
Percentage of benchmark derived from specified source	93.00%	15.00%
Current liabilities denominated in RMB	$104,800	$56,200
Advertising & Marketing | Consolidated net revenues benchmark | Customer concentration risk | Top 10 advertising agencies | China
Concentration of risks
Number of advertising agencies	10	10
Percentage of benchmark derived from specified source	14.00%	20.00%

Investment_in_Weibo_Details

Investment in Weibo (Details) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2014	Apr. 30, 2014	Apr. 29, 2013	Apr. 17, 2014	Apr. 16, 2014
Investment in Weibo
Carrying Amount		$479,612,000
Stock-based compensation charge recorded to reflect the difference between the proceeds received by employees and the fair value of the employee vested shares sold	13,779,000	31,242,000	1,837,000
Investor option liability		29,504,000
Income (losses) recognized as subsequent change in fair value of investor option liability	-46,972,000	21,064,000
Amount due to SINA	1,717,000	267,722,000
IPO
Investment in Weibo
Amount invested in Weibo	301,278,000
Convertible preferred shares
Investment in Weibo
Carrying Amount		479,612,000						479,612,000
Shares outstanding		30,046,000						30,046,154
Class A ordinary shares | IPO
Investment in Weibo
Issuance of shares (in shares)				19,320,000
SINA
Investment in Weibo
Number of shares repurchased					2,923,478
Payment for repurchase of ordinary shares					42,200,000
Deemed contribution due to discount of share price	61,176,000
Amount due to SINA	1,717,000	267,722,000
Interest amount waived		8,500,000
SINA | Amount due to SINA
Investment in Weibo
Interest rate, minimum	2.55%
Interest rate, maximum	3.05%
Loan payable to SINA						250,000,000
Amount due to SINA	1,700,000	267,700,000				250,000,000
Interest amount waived						8,500,000
Alibaba
Investment in Weibo
Amount invested in Weibo	42,224,000	39,038,000
Stock-based compensation charge recorded to reflect the difference between the proceeds received by employees and the fair value of the employee vested shares sold		27,100,000
Deemed contribution due to discount of share price	15,300,000
Alibaba
Investment in Weibo
Amount invested in Weibo						585,800,000
Ownership interest on a fully diluted basis (as a percent)						18.00%
Maximum percentage of ownership interest to be reached under option granted						30.00%	30.00%
Threshold percentage of sale of shares including prior sales considered for expiration of option to increase ownership interest						25.00%
Investor option liability						50,600,000		76,500,000
Income (losses) recognized as subsequent change in fair value of investor option liability	-47,000,000	21,100,000	0
Alibaba | Convertible preferred shares
Investment in Weibo
Issuance of shares (in shares)						30,000,000
Fair value of preferred shares						481,000,000
Alibaba | Class A ordinary shares
Investment in Weibo
Issuance of shares (in shares)						4,800,000
Number of ordinary shares acquired by investor							29,990,778
Initial fair value of ordinary shares recognized as non-controlling interest						54,200,000
Number of vested options repurchased						3,500,000
Stock-based compensation charge recorded to reflect the difference between the proceeds received by employees and the fair value of the employee vested shares sold		27,100,000
Percentage of discount applied on IPO offering price per share to calculate exercise price of option						15.00%
Threshold amount of equity valuation considered to calculate exercise price of option						$5,500,000,000
Alibaba | Class A ordinary shares | IPO
Investment in Weibo
Number of ordinary shares acquired by investor							6,000,000
Alibaba | SINA
Investment in Weibo
Number of ordinary shares acquired by investor							23,990,778
Percentage discount to IPO price applied to the shares acquired							15.00%
Alibaba | SINA | IPO
Investment in Weibo
Percentage discount to IPO price applied to the shares acquired							15.00%
Alibaba | SINA | Class A ordinary shares
Investment in Weibo
Number of ordinary shares acquired by investor							21,067,300
Alibaba | SINA | Class A ordinary shares | Private placement
Investment in Weibo
Number of ordinary shares acquired by investor							2,923,478
Percentage of discount applied on IPO offering price per share to calculate exercise price of option							15.00%

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents and Short-term Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and cash equivalents:
Cash	$53,512,000	$13,332,000
Cash equivalents:
Bank time deposits	229,950,000	233,104,000
Total cash and cash equivalents	283,462,000	246,436,000	2,906,000	13,688,000
Short-term investments:
Bank time deposits	166,414,000	252,342,000
Total cash, cash equivalents and short-term investments	449,876,000	498,778,000
Interest income	$8,300,000	$3,800,000

Longterm_Investments_and_Acqui1

Long-term Investments and Acquisition (Details) (USD $)	12 Months Ended			1 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-13
Long-term investments
Balance at the beginning of the period	$5,500	$3,565	$4,905
Loss from equity method investment		-1,236	-1,340
Investments made	41,766	10,135
Remeasurement gain upon obtaining control		3,116
Transfer from long-term investments to a wholly owned subsidiary		-10,080
Unrealized loss	-2,067
Balance at the end of period	45,199	5,500	3,565
Cost Method
Long-term investments
Balance at the beginning of the period	5,500
Investments made	26,670	5,500
Balance at the end of period	32,170	5,500
Equity Method
Long-term investments
Balance at the beginning of the period		3,565	4,905
Loss from equity method investment		-1,236	-1,340
Investments made		4,635
Remeasurement gain upon obtaining control		3,116
Transfer from long-term investments to a wholly owned subsidiary		-10,080
Balance at the end of period			3,565
Available-for-Sale Securities
Long-term investments
Investments made	15,096
Unrealized loss	-2,067
Balance at the end of period	13,029
SINA | Weibo Interactive
Long-term investments
Remeasurement gain upon obtaining control				3,100
Remaining equity interest acquired (as a percent)				45.00%
Cash consideration for remaining equity interest				$4,635

Longterm_Investments_and_Acqui2

Long-term Investments and Acquisition (Details 2) (USD $)	12 Months Ended	1 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	31-May-13	Dec. 31, 2014
Long term investments and step up acquisition
Remeasurement gain upon obtaining control	$3,116,000
Goodwill	7,517,000	7,517,000		11,652,000
SINA | Transfer of Equity Interest in Weibo Interactive
Long term investments and step up acquisition
Percentage of equity interest transferred to Group		100.00%
Consideration for transfer of equity interest to Group		10,100,000
Weibo Interactive | SINA
Long term investments and step up acquisition
Cash consideration for remaining equity interest			4,600,000
SINA | Weibo Interactive
Long term investments and step up acquisition
Equity interest previously held (as a percent)			55.00%
Remeasurement gain upon obtaining control			3,100,000
Remaining equity interest acquired (as a percent)			45.00%
Cash consideration for remaining equity interest			4,635,000
Fair value of previously held 55% equity interest			5,445,000
Total consideration			10,080,000
Tangible assets			98,000
Identifiable intangible assets acquired			3,560,000
Liabilities assumed			-1,095,000
Goodwill			7,517,000
Total consideration			10,080,000
SINA | Weibo Interactive | Minimum
Long term investments and step up acquisition
Estimated useful life of identifiable intangible assets acquired			2 years
SINA | Weibo Interactive | Maximum
Long term investments and step up acquisition
Estimated useful life of identifiable intangible assets acquired			5 years
SINA | Weibo Interactive | Customer list
Long term investments and step up acquisition
Identifiable intangible assets acquired			2,100,000
SINA | Weibo Interactive | Game platform technology
Long term investments and step up acquisition
Identifiable intangible assets acquired			1,000,000
SINA | Weibo Interactive | Non-compete agreement
Long term investments and step up acquisition
Identifiable intangible assets acquired			$500,000

Longterm_Investments_and_Acqui3

Long-term Investments and Acquisition (Details 3) (USD $)	1 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill		$11,652	$7,517
Gametree
Business Acquisition [Line Items]
Remaining equity interest acquired (as a percent)	84.00%
Cash consideration for remaining equity interest	3,062
Non-controlling interests	292
Total consideration	3,354
Tangible assets	1,518
Identifiable intangible assets acquired	1,688
Liabilities assumed	-3,692
Goodwill	3,840
Total consideration	$3,354
Gametree | Game platform technology
Business Acquisition [Line Items]
Estimated useful life of identifiable intangible assets acquired	4 years 3 months 18 days

Longterm_Investments_and_Acqui4

Long-term Investments and Acquisition (Details 4) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2014	Dec. 31, 2012
Changes in the group's goodwill by segment
Balance at the beginning of the period	$7,517
Others	295
Balance at the end of the period	11,652
Weibo Interactive
Changes in the group's goodwill by segment
Acquisition		7,517
Gametree
Changes in the group's goodwill by segment
Balance at the beginning of the period			3,840
Acquisition	3,840
Balance at the end of the period			3,840
Advertising & Marketing
Changes in the group's goodwill by segment
Balance at the beginning of the period	0			0
Others	0
Balance at the end of the period	0			0
Advertising & Marketing | Weibo Interactive
Changes in the group's goodwill by segment
Acquisition		0
Advertising & Marketing | Gametree
Changes in the group's goodwill by segment
Acquisition	0
Other
Changes in the group's goodwill by segment
Balance at the beginning of the period	7,517
Others	295
Balance at the end of the period	11,652
Other | Weibo Interactive
Changes in the group's goodwill by segment
Acquisition		7,517
Other | Gametree
Changes in the group's goodwill by segment
Acquisition	$3,840

Longterm_Investments_and_Acqui5

Long-term Investments and Acquisition (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Long-term Investments and Acquisition
Intangible assets, net	$3,539,000	$3,071,000
Amortization expense	1,200,000	200,000
2015	1,498,000
2016	769,000
2017	688,000
2018	584,000
2019 and thereafter	0
Total expected amortization expense	$3,539,000

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended
	Aug. 31, 2010	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
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
2010 Plan | Stock options
Stock-based compensation
Percentage of ordinary shares outstanding, granted		0.00%	1.70%	1.30%
Estimated fair value of options at grant date		0	$16,900,000	$3,600,000
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		10.00%

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation
Stock-based compensation expense	$13,779,000	$31,242,000	$1,837,000
Amortization period	4 years
Stock compensation expenses related to the grants	13,800,000	4,100,000	1,800,000
Alibaba
Stock-based compensation
Stock-based compensation expense		27,100,000
Costs of revenues
Stock-based compensation
Stock-based compensation expense	755,000	4,253,000	201,000
Sales and marketing
Stock-based compensation
Stock-based compensation expense	1,583,000	6,150,000	330,000
Product development
Stock-based compensation
Stock-based compensation expense	4,392,000	9,209,000	638,000
General and administrative
Stock-based compensation
Stock-based compensation expense	$7,049,000	$11,630,000	$668,000

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Number of shares available for issuance
Outstanding number of shares available for issuance at the beginning of the period	4,648,000	8,086,000	6,728,000
Addition (2014 plan)	1,000,000
Granted (in shares or equivalent shares)	-2,951,000	-4,772,000	-2,175,000
Cancelled/expired/forfeited (in shares)	41,000	1,157,000	908,000
Repurchased (in shares)		177,000	2,625,000
Outstanding number of shares available for issuance at the end of the period	2,738,000	4,648,000	8,086,000
Aggregate Intrinsic Value
Fair value per ordinary share (in dollars per share)	$14.24	$14.10
Stock options
Assumptions used to value the option grants
Expected volatility, minimum (as a percent)		54.00%	60.00%
Expected volatility, maximum (as a percent)		61.00%	63.00%
Risk-free interest rate, Minimum (as a percent)		0.50%	0.40%
Risk-free interest rate, Maximum (as a percent)		1.20%	0.80%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Number of shares available for issuance
Granted (in shares or equivalent shares)		-1,400,000
Stock options activity
Outstanding at the beginning of the period (in shares)	18,561,000	23,469,000	28,272,000
Granted (in shares)	0	3,372,000	2,175,000
Exercise (in shares)	-3,697,000	-3,449,000	-3,445,000
Cancelled/expired/forfeited (in shares)	-534,000	-1,157,000	-908,000
Repurchased (in shares)		-3,674,000	-2,625,000
Outstanding at the end of the period (in shares)	14,330,000	18,561,000	23,469,000	28,272,000
Vested and expected to vest at the end of the year (in shares)	14,261,000	18,261,000
Exercisable at the end of the period (in shares)	11,446,000	8,957,000
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$1.17	$0.69	$0.41
Granted (in dollars per share)		$3.38	$3.34
Exercise (in dollars per share)	$0.52	$0.38	$0.36
Cancelled/expired/forfeited (in dollars per share)	$2.84	$2.49	$0.60
Repurchased (in dollars per share)		$0.45	$0.36
Outstanding at the end of the period (in dollars per share)	$1.28	$1.17	$0.69	$0.41
Vested and expected to vest at the end of the period (in dollars per share)	$1.27	$1.14
Exercisable at the end of the period (in dollars per share)	$0.76	$0.48
Weighted Average Remaining Contractual Life
Outstanding at the end the period	3 years 2 months 12 days	4 years 3 months 18 days	4 years 7 months 6 days	5 years 6 months
Vested and expected to vest at the end of the period	3 years 2 months 12 days	4 years 3 months 18 days
Exercisable at the end of the period	2 years 8 months 12 days	3 years 8 months 12 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$185,684,000	$239,975,000	$60,226,000	$82,726,000
Vested and expected to vest at the end of the period	184,937,000	236,716,000
Exercisable at the end of the period	154,235,000	122,026,000
Total intrinsic value of options exercised	65,700,000	37,300,000	10,300,000
Cash received from the exercises of stock option	1,500,000	1,000,000	0
Unrecognized compensation cost	$11,300,000	$16,400,000
Weighted-average period of unrecognized compensation cost	2 years 2 months 12 days
Stock options | 2010 Plan
Stock options activity
Granted (in shares)		3,400,000
Stock options | 2014 Plan
Stock options activity
Granted (in shares)	0
Stock options | Minimum
Assumptions used to value the option grants
Expected term		3 years 6 months	3 years 6 months
Stock options | Maximum
Assumptions used to value the option grants
Expected term		4 years 9 months 18 days	4 years 9 months 18 days
Restricted share units
Number of shares available for issuance
Restricted shares units granted (in shares)	3,000,000	800,000

StockBased_Compensation_Detail3

Stock-Based Compensation (Details 4) (Stock options, USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Range of Exercise Prices
Options Outstanding (in shares)	14,330	18,561
Weighted Average Exercise Price (in dollars per share)	$1.28	$1.17
Options Exercisable (in shares)	11,446	8,957
Weighted Average Exercise Price (in dollars per share)	$0.76	$0.48
Weighted Average Remaining Contractual Life	3 years 2 months 12 days	4 years 3 months 18 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	$0.36
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$0.41	$0.41
Options Outstanding (in shares)	9,337	12,571
Weighted Average Exercise Price (in dollars per share)	$0.37	$0.36
Options Exercisable (in shares)	9,337	7,989
Weighted Average Exercise Price (in dollars per share)	$0.37	$0.36
Weighted Average Remaining Contractual Life	2 years 3 months 18 days	3 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)	844	1,324
Weighted Average Exercise Price (in dollars per share)	$1.19	$1.14
Options Exercisable (in shares)	764	830
Weighted Average Exercise Price (in dollars per share)	$1.18	$1.14
Weighted Average Remaining Contractual Life	3 years 1 month 6 days	4 years 3 months 18 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)	2,542	2,822
Weighted Average Exercise Price (in dollars per share)	$3.29	$3.30
Options Exercisable (in shares)	1,345	138
Weighted Average Exercise Price (in dollars per share)	$3.30	$3.26
Weighted Average Remaining Contractual Life	4 years 9 months 18 days	5 years 7 months 6 days
$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)	1,607	1,844
Weighted Average Exercise Price (in dollars per share)	$3.48	$3.48
Weighted Average Remaining Contractual Life	5 years 6 months	6 years 7 months 6 days

StockBased_Compensation_Detail4

Stock-Based Compensation (Details 5) (Service-based restricted share units, USD $)	12 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Service-based restricted share units
Restricted Share Units
Outstanding at the beginning of the period (in shares)	800
Awarded (in shares)	2,951
Vested (in shares)	-203
Cancelled (in shares)	-41
Outstanding at the end of the period (in shares)	3,507	800
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$13.19
Awarded (in dollars per share)	$17.11
Vested (in dollars per share)	$13.19
Cancelled (in dollars per share)	$17.23
Outstanding at the end of the period (in dollars per share)	$16.44	$13.19
Unrecognized compensation cost	$47,700,000
Expected weighted-average recognition period for unrecognized compensation cost	3 years 6 months
Total fair value vested	$2,700,000	$0

Other_Balance_Sheet_Components2

Other Balance Sheet Components (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts receivable, net:
Total gross amount	$122,650	$50,546
Allowance for doubtful accounts:
Balance at the beginning of the year	-3,242	-897
Additional provision charged to expenses	-2,138	-2,345	-897
Write-off	2,940
Balance at the end of the year	-2,440	-3,242	-897
Accounts receivable, net	120,210	47,304
Prepaid expenses and other current assets:
Rental and other deposits	3,319	3,244
Current deferred tax assets	18	744
Input VAT	1,526
Prepayment for long-term investments	1,942	495
Advertising prepayment	3,936
Prepayment to outsource service providers	1,730
Prepayment for license fee	1,872
Others	1,761	1,210
Prepaid expenses and other current assets	16,104	5,693
SINA and other related parties
Accounts receivable, net:
Total gross amount	18,648	2,058
Allowance for doubtful accounts:
Balance at the end of the year	-139	-228
Accounts receivable, net	18,509	1,830
Alibaba
Accounts receivable, net:
Total gross amount	64,725	21,299
Allowance for doubtful accounts:
Accounts receivable, net	64,725	21,299
Third parties
Accounts receivable, net:
Total gross amount	39,277	27,189
Allowance for doubtful accounts:
Balance at the end of the year	-2,301	-3,014
Accounts receivable, net	$36,976	$24,175

Other_Balance_Sheet_Components3

Other Balance Sheet Components (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property and equipment, net:
Property and equipment, gross	$96,795	$81,065
Less: Accumulated depreciation	-65,921	-45,363
Property and equipment, net	30,874	35,702
Accrued liabilities:
Payroll and welfare	19,686	7,336
Amounts owed on option/share repurchase	1,203	12,073
Content fees (including amounts due to related parties of $486 and nil as of December 31, 2013 and 2014)	1,005	572
Marketing expenses (including amounts due to related parties of $3,021 and 5,786 as of December 31, 2013 and 2014)	19,806	11,288
Internet connection costs	6,834	1,591
Employee payroll withholding taxes	3,547	3,950
Sales rebates	14,126	7,007
Advertisement production costs		2,774
Professional fees	3,138	912
Revenue share	3,057	3,097
VAT and other tax payable	6,629	702
Payable to other service providers	1,074	1,800
Payable to outsourced service providers	1,375	671
Others	5,998	2,641
Total Accrued liabilities	87,478	56,414
Content fees due to related parties	0	486
Marketing expenses due to related parties	5,786	3,021
Computers and equipment
Property and equipment, net:
Property and equipment, gross	89,069	74,843
Leasehold improvements
Property and equipment, net:
Property and equipment, gross	4,944	4,340
Furniture and fixtures
Property and equipment, net:
Property and equipment, gross	2,052	1,490
Other.
Property and equipment, net:
Property and equipment, gross	$730	$392

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended							0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Feb. 22, 2008
	jurisdiction
Income taxes
Number of tax jurisdictions	2
Components of loss before income taxes
Loss before income tax expenses (benefits)	($61,506,000)	($37,844,000)	($104,037,000)
Loss from non-China operations	-54,073,000	-13,341,000	-2,950,000
Loss from China operations	-7,433,000	-24,503,000	-101,087,000
Income tax expenses (benefits) applicable to China operations	1,128,000	271,000	-1,551,000
Effective tax rate for China operations (as a percent)	-15.20%	-1.10%	1.50%
Loss from the change in fair value of investor option liability	46,972,000	-21,064,000
Statutory EIT rate (as a percent)	25.00%	25.00%	25.00%
Net operating loss carryforwards	168,300,000	199,200,000
Composition of income tax expenses for China operations
Deferred tax expenses (benefits)	866,000	271,000	-1,551,000
Current income tax expenses	262,000
Income tax expenses (benefits)	1,128,000	271,000	-1,551,000
Reconciliation of the differences between statutory tax rate and the effective tax rate for China operations
Permanent differences (as a percent)	3.00%	0.60%	3.20%
Change in valuation allowance (as a percent)	6.80%	23.30%	23.30%
Effective tax rate for China operations (as a percent)	-15.20%	-1.10%	1.50%
Tax holiday effect	0
Deferred tax assets:
Net operating loss carry forwards	42,096,000	49,800,000
Less: valuation allowance	-42,065,000	-48,577,000
Net deferred tax assets	31,000	1,223,000
Including - Current deferred tax assets	18,000	744,000
Non-current deferred tax assets	13,000	479,000
Deferred tax liabilities:
Acquired intangible assets	873,000	768,000
Total deferred tax liabilities	873,000	768,000
Historical rate for valuing deferred tax assets (as a percent)	25.00%
Operating loss carryforwards provided with valuation allowance		194,400,000
Operating loss carryforwards expected to be utilized prior to expiration		4,800,000
Hong Kong
Components of loss before income taxes
Statutory EIT rate (as a percent)	16.50%
Net operating loss carryforwards	2,100,000
China
Components of loss before income taxes
Statutory EIT rate (as a percent)	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%	25.00%
Withholding income tax on dividends distributed by subsidiaries to its immediate holding entity outside China (as a percent)	10.00%
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%
China | Software enterprise
Components of loss before income taxes
Period of special tax holidays								2 years
Reduction in preferential tax rate (as a percent)								50.00%
Preferential statutory rate (as a percent)								12.50%
Period of reduced preferential income tax rate								3 years
Non- China
Components of loss before income taxes
Loss from the change in fair value of investor option liability	$47,000,000

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	31-May-13
Related party transactions
Deemed contribution from SINA	$61,176,000	$13,092,000
Legal transfer of Weibo Interactive and recognition of due to SINA		10,080,000
Costs and expenses allocated from SINA	42,360,000	44,305,000	43,960,000
Interest expense on amount due to SINA	2,838,000	6,709,000	4,923,000
Repayment of amount due to SINA	269,042,000	159,816,000
Amount of game platform maintenance service from Weibo Interactive	0	0	3,484,000
Outstanding balance due to or from related parties
Amount due to SINA	1,717,000	267,722,000		267,722,000
Accrued liabilities due to related parties	5,786,000	3,507,000		3,507,000
Amount of promotional services from related parties	11,160,000	878,000	0
SINA
Related party transactions
Deemed contribution from SINA	61,176,000	13,092,000
Legal transfer of Weibo Interactive and recognition of due to SINA		10,080,000
Costs and expenses allocated from SINA	42,360,000	44,305,000	43,960,000
Other costs and expenses billed by SINA	15,100,000
Interest expense on amount due to SINA	2,838,000	6,709,000	4,923,000
Repayment of amount due to SINA	276,614,000	159,816,000
Interest waived		8,500,000
Deemed contribution from related party	61,176,000
Outstanding balance due to or from related parties
Amount due to SINA	1,717,000	267,722,000		267,722,000
Accounts receivable due from related parties	3,151,000	1,830,000		1,830,000
Accrued liabilities due to related parties		3,507,000		3,507,000
SINA | Transfer of Equity Interest in Weibo Interactive
Related party transactions
Percentage of equity interest transferred to Group				100.00%
Consideration for transfer of equity interest to Group				10,100,000
SINA | Weibo Interactive
Related party transactions
Consideration for step-up acquisition					4,600,000
Alibaba
Related party transactions
Advertising and marketing revenues from related party	107,587,000	49,135,000
Deemed contribution from related party	15,300,000
Outstanding balance due to or from related parties
Accounts receivable due from related parties	64,725,000	21,299,000		21,299,000
Weibo Interactive
Related party transactions
Amount of game platform maintenance service from Weibo Interactive		0	3,500,000
Other related parties
Related party transactions
Advertising and marketing revenues from related party	27,551,000	2,315,000
Outstanding balance due to or from related parties
Other revenues from related party	1,500,000	0	0
Amount of promotional services from related parties	11,200,000	900,000	0
Due from related parties	15,400,000	0		0
Due to related parties	$5,800,000	$0		$0

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (China Contribution Plan, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
China Contribution Plan
Employee Benefit Plans
Employer contribution under China Contribution Plan	$27.20	$18.30	$14

Loss_Per_Share_Details

Loss Per Share (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net loss attributable to ordinary shareholders	($63,378)	($38,115)	($102,486)
Denominator:
Weighted average ordinary shares outstanding	186,878,000	146,820,000	140,831,000
Basic net loss per share attributable to ordinary shareholders (in dollars per share)	($0.34)	($0.26)	($0.73)
Numerator:
Net loss attributable for calculating diluted net loss per share	($63,378)	($38,115)	($102,486)
Denominator:
Weighted average ordinary shares outstanding	186,878,000	146,820,000	140,831,000
Weighted average ordinary shares equivalents:
Shares used in computing diluted net loss per share attributable to ordinary shareholders	186,878,000	146,820,000	140,831,000
Diluted net loss per share attributable to ordinary shareholders (in dollars per share)	($0.34)	($0.26)	($0.73)
Options and RSUs
Anti-dilutive share
Anti-dilutive share excluded from the calculation of diluted net income (loss) per share	17,800,000	52,600,000	23,500,000
Convertible preferred shares
Anti-dilutive share
Anti-dilutive share excluded from the calculation of diluted net income (loss) per share	0	30,000,000	0

Segment_Information_Details

Segment Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	segment
Summary information by segment
Number of principal business segments	2
Revenues	$334,172	$188,313	$65,929
Advertising & Marketing
Summary information by segment
Revenues	264,782	148,426	51,049
Other
Summary information by segment
Revenues	$69,390	$39,887	$14,880

Profit_Appropriation_and_Restr1

Profit Appropriation and Restricted Net Assets (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
	fund
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	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%
Transfer to non-distributable reserve funds	$0.10	$0
Net assets subject to restriction for the Group	$163

Financial_Instruments_Details

Financial Instruments (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014
Fair Value of Financial Instruments
Investor option liability	-29,504
Financial instruments measured on a recurring basis
Fair Value of Financial Instruments
Bank time deposits	485,446	396,364
Investor option liability	-29,504
Available-for-sale securities		13,029
Total	455,942	409,393
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		13,029
Total		13,029
Financial instruments measured on a recurring basis | Significant Other Observable Inputs (Level 2)
Fair Value of Financial Instruments
Bank time deposits	485,446	396,364
Total	485,446	396,364
Financial instruments measured on a recurring basis | Significant Unobservable Inputs (Level 3)
Fair Value of Financial Instruments
Investor option liability	-29,504
Total	-29,504
Financial instruments measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Alibaba
Fair Value of Financial Instruments
Percentage of ownership interest in subsidiary to be reached if fully exercised	30.00%

Financial_Instruments_Details_

Financial Instruments (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 16, 2014	Apr. 29, 2013
Key inputs used in investor option liability valuation
Fair value per ordinary share (in dollars per share)	$14.24	$14.10
Investor option liability		$29,504,000
Income (losses) recognized as subsequent change in fair value of investor option liability	-46,972,000	21,064,000
Financial instruments measured on a recurring basis
Key inputs used in investor option liability valuation
Investor option liability		29,504,000
Financial instruments measured on a recurring basis | Investor option liability
Key inputs used in investor option liability valuation
Risk-free interest rate (as a percent)		0.30%
Expected volatility (as a percent)		53.00%
Expected life (in years)		1 year 4 months 24 days
Fair value per ordinary share (in dollars per share)		$14.10
Investor option liability				76,500,000	50,600,000
Income (losses) recognized as subsequent change in fair value of investor option liability	-47,000,000	21,100,000
Financial instruments measured on a recurring basis | Investor option liability | Alibaba
Key inputs used in investor option liability valuation
Minimum percentage of shares sold (as a percent)		25.00%
Non-recurring
Key inputs used in investor option liability valuation
Impairment loss for investments under cost method	0	0	0
Impairment loss for investments under equity method	0	0	0
Impairment loss for available-for-sale investments	$0	$0	$0

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	item
Commitments and Contingencies
Rental expense of operating lease	$14,900,000	$8,800,000	$6,800,000
Operating lease commitments
Total	19,789,000
Less than One Year	11,489,000
One to Three Years	8,300,000
Three to Five Years	0
More than Five Years	0
Purchase commitments
Total	65,265,000
Less than One Year	58,498,000
One to Three Years	6,528,000
Three to Five Years	123,000
More than Five Years	$116,000
Number of claims, lawsuits, investigations and proceedings, including unasserted claims that are probable to be assessed, are likely to have, a material change on the Company's financial position results of operations or cash flow	0

Additional_informationcondense2

Additional information-condensed financial statements of Weibo Corporation (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 16, 2014
Additional information-condensed financial statements of Weibo Corporation
Minimum percentage of after-tax profit to reserve fund	10.00%
Current assets:
Cash and cash equivalents	$283,462	$246,436	$2,906	$13,688
Short-term investments	166,414	252,342
Prepaid expenses and other current assets	16,104	5,693
Total current assets	586,190	551,775
Total assets	677,781	606,934
LIABILITIES, MEZZANINE EQUITY AND SHAREHOLDERS' DEFICIT
Accrued liabilities	87,478	56,414
Amount due to SINA	1,717	267,722
Investor option liability		29,504
Total current liabilities	112,572	369,495
Commitments and contingencies
Mezzanine equity
Total mezzanine equity		479,612
Shareholders' equity (deficit):
Ordinary shares: $0.00025 par value; 600,000 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; 150,392 and 203,658 shares (including 87,649 Class A ordinary shares and 116,009 Class B ordinary shares) issued and outstanding as of December 31, 2013 and 2014, respectively.	51	37
Additional paid-in capital	904,402	31,352
Accumulated other comprehensive income (loss)	-2,943	521
Accumulated deficit	-338,229	-274,851
Total Weibo shareholders' equity (deficit)	563,281	-242,941
Total liabilities, mezzanine equity and shareholders' equity	677,781	606,934
Convertible preferred shares
Mezzanine equity
Total mezzanine equity		479,612			479,612
Weibo Corporation
Current assets:
Cash and cash equivalents	229,950	182,871	38	9,082
Short-term investments	166,253	252,342
Prepaid expenses and other current assets	229
Total current assets	396,432	435,213
Long-term investments	13,029
Investment in subsidiaries and VIE	160,577	105,815	25,361
Total assets	570,038	541,028
LIABILITIES, MEZZANINE EQUITY AND SHAREHOLDERS' DEFICIT
Accrued liabilities	6,543	15,650
Amount due to SINA	214	259,203
Investor option liability		29,504
Total current liabilities	6,757	304,357
Commitments and contingencies
Mezzanine equity
Total mezzanine equity		479,612
Shareholders' equity (deficit):
Ordinary shares: $0.00025 par value; 600,000 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; 150,392 and 203,658 shares (including 87,649 Class A ordinary shares and 116,009 Class B ordinary shares) issued and outstanding as of December 31, 2013 and 2014, respectively.	51	37
Additional paid-in capital	904,402	31,352
Accumulated other comprehensive income (loss)	-2,943	521
Accumulated deficit	-338,229	-274,851
Total Weibo shareholders' equity (deficit)	563,281	-242,941
Total liabilities, mezzanine equity and shareholders' equity	570,038	541,028
Weibo Corporation | Convertible preferred shares
Mezzanine equity
Total mezzanine equity		$479,612

Additional_informationcondense3

Additional information-condensed financial statements of Weibo Corporation (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Apr. 16, 2014
Balance sheets
Ordinary shares, par value (in dollars per share)	$0.00	$0.00
Ordinary shares, shares authorized	2,400,000,000	600,000,000
Ordinary shares, shares issued	203,658,000	150,392,000
Ordinary shares, shares outstanding	203,658,000	150,392,000
Convertible preferred shares
Balance sheets
Convertible preferred shares, par value (in dollars per share)		$0.00
Convertible preferred shares, shares authorized		100,000,000
Convertible preferred shares, shares issued		30,046,000
Convertible preferred shares, shares outstanding		30,046,000	30,046,154
Convertible preferred shares, redemption value (in dollars per share)		$16.79
Class A ordinary shares
Balance sheets
Ordinary shares, shares authorized	1,800,000,000
Ordinary shares, shares issued	87,649,000
Ordinary shares, shares outstanding	87,649,000
Class B ordinary shares
Balance sheets
Ordinary shares, shares authorized	200,000,000
Ordinary shares, shares issued	116,009,000
Ordinary shares, shares outstanding	116,009,000
Ordinary shares to be designated
Balance sheets
Ordinary shares, shares authorized	400,000,000
Weibo Corporation
Balance sheets
Ordinary shares, par value (in dollars per share)	$0.00	$0.00
Ordinary shares, shares authorized	2,400,000,000	600,000,000
Ordinary shares, shares issued	203,658,000	150,392,000
Ordinary shares, shares outstanding	203,658,000	150,392,000
Weibo Corporation | Convertible preferred shares
Balance sheets
Convertible preferred shares, par value (in dollars per share)		$0.00
Convertible preferred shares, shares authorized	0	100,000,000
Convertible preferred shares, shares issued	0	30,046,000
Convertible preferred shares, shares outstanding	0	30,046,000
Convertible preferred shares, redemption value (in dollars per share)	$0	$16.79
Weibo Corporation | Class A ordinary shares
Balance sheets
Ordinary shares, shares authorized	1,800,000,000
Ordinary shares, shares issued	87,649,000
Ordinary shares, shares outstanding	87,649,000
Weibo Corporation | Class B ordinary shares
Balance sheets
Ordinary shares, shares authorized	200,000,000
Ordinary shares, shares issued	116,009,000
Ordinary shares, shares outstanding	116,009,000
Weibo Corporation | Ordinary shares to be designated
Balance sheets
Ordinary shares, shares authorized	400,000,000

Additional_informationcondense4

Additional information-condensed financial statements of Weibo Corporation (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statements of loss and comprehensive loss
Operating loss	($21,292,000)	($57,904,000)	($97,844,000)
Interest and other income (expenses), net	6,758,000	-2,884,000	-4,853,000
Change in fair value of investor option liability (Note 14)	-46,972,000	21,064,000
Other loss, net
Share of loss of subsidiaries and VIE		-1,236,000	-1,340,000
Net loss attributable to Weibo	-63,378,000	-38,115,000	-102,486,000
Other comprehensive income (loss)
Available-for-sale fair value change	-2,067,000
Comprehensive loss attributable to Weibo's ordinary shareholders	-66,842,000	-38,487,000	-102,468,000
Weibo Corporation
Statements of loss and comprehensive loss
Operating loss	-1,086,000	-31,764,000	-1,841,000
Interest and other income (expenses), net	5,034,000	-2,051,000	-4,923,000
Change in fair value of investor option liability (Note 14)	-46,972,000	21,064,000
Other loss, net
Share of loss of subsidiaries and VIE	-20,354,000	-25,364,000	-95,722,000
Net loss attributable to Weibo	-63,378,000	-38,115,000	-102,486,000
Other comprehensive income (loss)
Currency translation adjustments attributable to Weibo	-1,397,000	-372,000	18,000
Available-for-sale fair value change	-2,067,000
Comprehensive loss attributable to Weibo's ordinary shareholders	($66,842,000)	($38,487,000)	($102,468,000)

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Additional information-condensed financial statements of Weibo Corporation (Details 4) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statements of cash flow
Net cash provided by (used in) operating activities	($24,679)	($9,369)	($103,642)
Net cash used in investing activities	21,045	-153,365	-136,526
Net cash provided by financing activities	42,695	406,753	229,368
Cash and cash equivalents at the beginning of the year	246,436	2,906	13,688
Cash and cash equivalents at the end of the year	283,462	246,436	2,906
Weibo Corporation
Statements of cash flow
Net cash provided by (used in) operating activities	13,152	-19,629	-3
Net cash used in investing activities	-6,701	-218,908	-117,564
Net cash provided by financing activities	40,628	421,370	108,523
Net increase (decrease) in cash and cash equivalents	47,079	182,833	-9,044
Cash and cash equivalents at the beginning of the year	182,871	38	9,082
Cash and cash equivalents at the end of the year	229,950	182,871	38
Supplemental schedule of non-cash investing and financing activities
Investment in subsidiaries and VIE directly financed by SINA (refund to SINA)*	($7,536)	$19,346	$121,083

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Additional information-condensed financial statements of Weibo Corporation (Details 5) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in investments
Share of loss of subsidiaries and VIE		($1,236)	($1,340)
Weibo Corporation
Change in investments
Balance at the beginning of the period	105,815	25,361
Additional investment made, net	75,116	105,818
Share of loss of subsidiaries and VIE	-20,354	-25,364	-95,722
Balance at the end of the period	$160,577	$105,815	$25,361