Qihoo 360 Technology (QIHU) 20-F 27 Apr 15 2014 FY Annual report (foreign) Financial data

Document_and_Entity_Informatio

Document and Entity Information	12 Months Ended
	Dec. 31, 2014
Document Information [Line Items]
Document Type	20-F
Entity Registrant Name	Qihoo 360 Technology Co Ltd
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Central Index Key	1508913
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Document Period End Date	31-Dec-14
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	147,485,168
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	45,931,163

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
ASSETS
Cash and cash equivalents	$1,645,234	$1,013,465
Restricted cash	2,053	2,368
Short-term investments	58,736	748
Accounts receivable (net of allowance for doubtful accounts of $145 and $2,410 as of December 31, 2013 and 2014, respectively)	154,287	54,598
Prepaid expenses and other current assets	221,196	80,538
Amounts due from related parties	9,799	2,871
Deferred tax assets - current	4,844	3,129
Total current assets	2,096,149	1,157,717
Property and equipment, net	272,026	163,864
Land use rights, net	139,107	75,698
Acquired intangible assets, net	51,289	17,248
Goodwill	344,630	29,509
Long-term investments	314,979	84,293
Other noncurrent assets	97,025	39,621
Deferred tax assets - noncurrent	16,365	946
Total assets	3,331,570	1,568,896
Current liabilities (including amounts of the consolidated VIEs without recourse to Qihoo 360 Technology Co. Ltd. of $137,611 and $367,837 as of December 31, 2013 and 2014, respectively):
Short-term loans	0	1,322
Accounts payable	121,115	25,030
Accrued expenses and other current liabilities	298,831	120,418
Deferred revenue-current	72,890	46,632
Amounts due to related parties	1,089	517
Income tax payable	46,304	14,679
Total current liabilities	540,229	208,598
Non-current liabilities (including amounts of the consolidated VIEs without recourse to Qihoo 360 Technology Co. Ltd. of $2,235 and $9,611 as of December 31, 2013 and 2014, respectively):
Deferred tax liabilities	8,516	2,676
Deferred revenue-noncurrent	2,281	3,544
Long-term debt	1,635,000	600,000
Other non-current liabilities	3,276	0
Total liabilities	2,189,302	814,818
Commitments and contingencies (Note 20)
EQUITY
Treasury stock	-139	-139
Additional paid-in capital	669,760	568,675
Statutory reserves	49,433	28,149
Accumulated other comprehensive income (loss)	-11,772	20,380
Retained earnings	321,123	119,639
Total Qihoo 360 Technology Co. Ltd. shareholders' equity	1,028,598	736,893
Noncontrolling interest	113,670	17,185
TOTAL EQUITY	1,142,268	754,078
TOTAL LIABILITIES AND EQUITY	3,331,570	1,568,896
Class A ordinary shares ($0.001 par value; 378,000,000 and 378,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 134,123,218 and 147,485,168 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	147	134
Class B ordinary shares ($0.001 par value; 122,000,000 and 122,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 54,767,703 and 45,931,163 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	$46	$55

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, except Share data, unless otherwise specified
Allowance for doubtful accounts	$2,410	$145	$213	$68
Current liabilities	540,229	208,598
Class A ordinary shares [Member]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	378,000,000	378,000,000
Ordinary shares, shares issued and outstanding	147,485,168	134,123,218
Class B ordinary shares [Member]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	122,000,000	122,000,000
Ordinary shares, shares issued and outstanding	45,931,163	54,767,703
VIEs without recourse to Qihoo 360 Technology Co. Ltd. [Member]
Current liabilities	367,837	137,611
Non-current liabilities	$9,611	$2,235

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Internet services	$1,370,695	$671,088	$328,882
Others	19,965	0	150
Total revenues	1,390,660	671,088	329,032
Cost of revenues:
Internet services	297,645	87,838	32,762
Others	7,817	0	40
Total cost of revenues	305,462	87,838	32,802
Subsidy income	8,506	2,349	2,570
Operating expenses:
Selling and marketing	333,701	110,104	58,178
General and administrative	94,260	117,148	35,643
Product development	406,250	255,248	156,269
Total operating expenses	834,211	482,500	250,090
Income from operations	259,493	103,099	48,710
Interest income	25,605	10,398	6,715
Interest expense	-25,518	-5,572	0
Other income	1,803	590	1,243
Exchange gain (loss)	-11,899	5,105	49
(Loss) gain in connection with short-term investments	10,230	327	-52
Gain in connection with long-term investments	26,780	11,216	2,464
Gain (loss) on disposal of subsidiaries	0	-1,144	3,566
Income before income tax expense and loss from equity method investments	286,494	124,019	62,695
Income tax expense	-51,425	-23,423	-11,379
Loss from equity method investments	-18,906	-2,747	-4,845
Net income	216,163	97,849	46,471
Add: Net loss attributable to noncontrolling interest	6,605	1,803	275
Net income attributable to Qihoo 360 Technology Co. Ltd.	222,768	99,652	46,746
Net income per ordinary share-basic (in dollars per share)	$1.20	$0.55	$0.26
Net income per ordinary share-diluted (in dollars per share)	$1.13	$0.52	$0.25
Weighted average shares used in calculating net income per ordinary share-basic (in shares)	185,107,216	180,476,681	176,442,866
Weighted average shares used in calculating net income per ordinary share-diluted (in shares)	197,491,372	193,036,850	183,623,235
Cost of revenues [Member]
Share-based compensation expense included in:
Allocated Share-based Compensation Expense	0	0	4
Selling and marketing [Member]
Share-based compensation expense included in:
Allocated Share-based Compensation Expense	15,571	15,389	21,260
General and administrative [Member]
Share-based compensation expense included in:
Allocated Share-based Compensation Expense	16,891	69,101	8,365
Product development [Member]
Share-based compensation expense included in:
Allocated Share-based Compensation Expense	$62,594	$36,597	$20,976

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$216,163	$97,849	$46,471
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	-17,210	11,104	2,849
Unrealized loss on available-for-sale investments	-15,876	0	0
Other comprehensive income (loss)	-33,086	11,104	2,849
Comprehensive income	183,077	108,953	49,320
Add: Comprehensive loss attributable to noncontrolling interest	7,539	1,965	277
Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.	$190,616	$110,918	$49,597

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Equity (USD $)	Total	Ordinary shares [Member]	Treasury stock [Member]	Additional paid-in capital [Member]	Statutory reserves [Member]	Accumulated other comprehensive income (loss) [Member]	(Accumulated deficit) retained earnings [Member]	Total Qihoo 360 Technology Co. Ltd. shareholders' equity [Member]	Noncontrolling interest [Member]
In Thousands, except Share data
Beginning Balance, amount at Dec. 31, 2011	$371,492	$179		$363,021	$5,667	$6,263	($4,277)	$370,853	$639
Beginning Balance, shares (in shares) at Dec. 31, 2011		179,029,251
Issuance of ordinary shares in connection with share-based compensation arrangements, shares (in shares)		3,512,394
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	3	3						3
Share-based compensation	50,605			50,605				50,605
Issuance of ordinary shares in connection with exercise of options, shares (in shares)		1,615,452
Issuance of ordinary shares in connection with exercise of options, amount	6,965	2		6,963				6,965
Provision for statutory reserves					10,408		-10,408
Noncontrolling interest for establishments of subsidiaries	422								422
Disposal of noncontrolling interest in subsidiaries	-544			73				73	-617
Net income	46,471						46,746	46,746	-275
Other comprehensive income (loss)	2,849					2,851		2,851	-2
Ending Balance, amount at Dec. 31, 2012	478,263	184		420,662	16,075	9,114	32,061	478,096	167
Ending Balance, shares (in shares) at Dec. 31, 2012		184,157,097
Issuance of ordinary shares in connection with share-based compensation arrangements, shares (in shares)		561,517
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	1	1						1
Share repurchase, shares (in shares)		-14,544
Share repurchase, amount	-139		-139					-139
Share-based compensation	121,087			121,087				121,087
Issuance of ordinary shares in connection with exercise of options, shares (in shares)		3,982,385
Issuance of ordinary shares in connection with exercise of options, amount	19,071	4		19,067				19,071
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)		204,466
Issuance of ordinary shares in connection with business acquisitions, amount	7,864			7,864				7,864
Provision for statutory reserves					12,074		-12,074
Addition of noncontrolling interest in connection with business acquisitions	18,868								18,868
Capital injection of non-controlling interest holders to a subsidiary	654								654
Disposal of noncontrolling interest in subsidiaries	-544			-5				-5	-539
Net income	97,849						99,652	99,652	-1,803
Other comprehensive income (loss)	11,104					11,266		11,266	-162
Ending Balance, amount at Dec. 31, 2013	754,078	189	-139	568,675	28,149	20,380	119,639	736,893	17,185
Ending Balance, shares (in shares) at Dec. 31, 2013		188,890,921
Issuance of ordinary shares in connection with share-based compensation arrangements, shares (in shares)		2,691,753
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	2						2
Share-based compensation	90,392			90,392				90,392
Issuance of ordinary shares in connection with exercise of options, shares (in shares)	1,833,657	1,833,657
Issuance of ordinary shares in connection with exercise of options, amount	15,066	2		15,064				15,066
Provision for statutory reserves					21,284		-21,284
Addition of noncontrolling interest in connection with business acquisitions	97,400								97,400
Capital injection of non-controlling interest holders to a subsidiary	32,000								32,000
Acquisition of additional equity interests in subsidiaries	-947			-4,371				-4,371	3,424
Net income	216,163						222,768	222,768	-6,605
Other comprehensive income (loss)	-33,086					-32,152		-32,152	-934
Ending Balance, amount at Dec. 31, 2014	$1,142,268	$193	($139)	$669,760	$49,433	($11,772)	$321,123	$1,028,598	$113,670
Ending Balance, shares (in shares) at Dec. 31, 2014		193,416,331

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$216,163	$97,849	$46,471
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation	95,056	121,087	50,605
Depreciation and amortization	82,531	42,629	16,457
(Gain) loss on disposal of property and equipment	1,088	213	-838
Amortization of land use rights	2,256	1,714	140
Loss from impairment of intangible assets	0	948	1,348
Provision of allowance for doubtful accounts	214	157	454
Loss (gain) in connection with short-term investments	-10,230	-327	52
Loss on equity method investments	18,906	2,747	4,845
Gain in connection with long-term investments	-26,780	-11,216	-2,464
(Gain) loss on disposal of subsidiaries	0	1,144	-3,566
Changes in operating assets and liabilities:
Accounts receivable	-88,957	-30,789	-6,765
Prepaid expenses and other current assets	-19,681	-40,271	-8,404
Amount due from related parties	-1,428	-1,645	0
Payment for land use rights	-55,103	-72,888	-14,102
Deferred taxes	-15,157	837	-1,204
Other noncurrent assets	184	-3,010	392
Accounts payable	83,219	18,796	1,164
Accrued expenses and other current liabilities	67,416	53,605	23,274
Deferred revenue	5,784	20,466	10,354
Amount due to related parties	232	366	83
Income tax payable	24,586	7,814	-508
Net cash provided by operating activities	380,299	210,226	117,788
Cash flows from investing activities:
(Increase) decrease in restricted cash	1,604	-431	-1,902
Purchase of property and equipment	-170,162	-118,334	-68,796
Proceeds from disposal of property and equipment	112	1	2,126
Purchase of intangible assets	-676	-3,068	-5,073
Purchase of other assets	0	0	-459
Purchase of short-term investments	-82,934	-997	0
Proceeds from disposal of short-term investments	41,798	762	0
Capital contribution for long-term investments	-325,000	-80,967	-24,241
Cash collected from disposal of long-term investments and a subsidiary	22,635	18,880	13,847
Dividends received from a cost method investee	0	413	313
Net cash (paid for) acquired from business acquisitions	-148,871	-9,827	258
Deconsolidation of a subsidiary	0	-3,306	0
Net cash used in investing activities	-661,494	-196,874	-83,927
Cash flows from financing activities:
Repayment for short-term loans	-13,907	0	0
Proceeds from short-term loans	4,523	1,314	0
Proceeds from issuance of Convertible Senior Notes (net of issuance costs of $12,150 and $18,630 in 2013 and 2014, respectively)	1,016,370	587,850	0
Proceeds from exercise of share options	15,947	23,678	2,089
Cash received from capital contribution by noncontrolling interest shareholders to subsidiaries	1,632	656	36
Cash paid to acquire additional equity interest in a subsidiary	-650	0	0
Payment for share repurchase	-104,201	0	-139
Net cash provided by financing activities	919,714	613,498	1,986
Effect of exchange rate on cash and cash equivalents	-6,750	5,951	1,086
Net increase in cash and cash equivalents	631,769	632,801	36,933
Cash and cash equivalents at beginning of year	1,013,465	380,664	343,731
Cash and cash equivalents at end of year	1,645,234	1,013,465	380,664
Supplemental disclosure of cash flow information:
Income tax paid	44,810	13,961	12,578
Interest expense paid	15,853	0	0
Supplemental schedule of non-cash activities:
Payable for interests of Convertible Senior Notes	10,062	4,808	0
Payable for purchasing land use rights, plant, property and equipment and intangible assets	15,507	20,861	125,760
Consideration payable in connection with business acquisitions	67,665	358	0
Issuance of ordinary shares for business acquisition		$7,864

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Parenthetical) (Convertible Senior Notes [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Convertible Senior Notes [Member]
Debt issuance costs	$18,630	$12,150

Organization_and_Principal_Act

Organization and Principal Activities	12 Months Ended
	Dec. 31, 2014
Organization and Principal Activities [Abstract]
Organization and Principal Activities		1	ORGANIZATION AND PRINCIPAL ACTIVITIES
	Qihoo 360 Technology Co. Ltd. (the "Company" or "Qihoo 360", formerly known as Qihoo Technology Company Limited), incorporated in the Cayman Islands in June 2005, with its consolidated subsidiaries, variable interest entities ("VIEs") and VIEs' subsidiaries (collectively referred to the "Group") is primarily involved in the operations of internet services in the People's Republic of China (the "PRC").
	As of December 31, 2014, the Company has wholly-owned and majority-owned subsidiaries incorporated in countries and jurisdictions including PRC, Hong Kong, U.S.A, Singapore and Japan. The Company's major subsidiaries are as follows:
		·	Qiji International Development Limited ("Qiji International")
		·	Qifei International Development Co. Limited ("Qifei International")
		·	360 International Development Co. Limited ("360 International")
		·	Qizhi Software (Beijing) Co., Ltd. ("Qizhi Software")
		·	Tianjin Qisi Technology Co., Ltd. ("Tianjin Qisi")
		·	Qifei Xiangyi (Beijing) Software Co., Ltd. ("Qifei Xiangyi")
	As of December 31, 2014, the Company also effectively controls VIEs under contractual arrangements. The major VIEs are as follows:
		·	Beijing Qihu Technology Co., Ltd. ("Beijing Qihu")
		·	Beijing Star World Technology Co., Ltd. ("Beijing Star World")
	The VIE arrangements
	PRC regulations currently limit direct foreign ownership of business entities providing internet services in the PRC where certain licenses are required for the provision of such services. To comply with these PRC regulations, the Company conducts substantially the majority of its business through the VIEs and their subsidiaries. To provide the Company the expected residual returns of the VIEs and their subsidiaries, Qizhi Software has entered into the following contractual arrangements with the VIEs and their shareholders that enable the Company to (1) have power to direct the activities that most significantly affect the economic performance of the VIEs, and (2) receive the economic benefits of the VIEs that could be significant to the VIEs. Accordingly, the Company is considered the primary beneficiary of the VIEs and has consolidated the VIEs' financial results of operations, assets and liabilities in the Company's consolidated financial statements. In making the conclusion that the Company is the primary beneficiary of the VIEs, the Company believes the Company's rights under the terms of the equity disposition agreements provide it with a substantive kick out right. More specifically, the Company believes the terms of the equity disposition agreements are valid, binding and enforceable under PRC laws and regulations currently in effect. A simple majority vote of the Company's board of directors is required to pass a resolution to exercise the Company's rights under the exclusive option agreement, for which the consent from the shareholders of the VIEs is not required. The Company's rights under the equity disposition agreements give the Company the power to control the shareholders of the VIEs and thus the power to direct the activities that most significantly impact the VIEs' economic performance. In addition, the Company's rights under the powers of attorney also reinforce the Company's abilities to direct the activities that most significantly impact the VIEs' economic performance. The Company also believes that this ability to exercise control ensures that the VIEs will continue to execute and renew service agreements and pay service fees to the Company. By charging service fees in whatever amounts the Company deems fit, and by ensuring that service agreements are executed and renewed indefinitely, the Company has the rights to receive substantially all of the economic benefits from the VIEs.
	The series of contractual arrangements are summarized as follows:
	Business operation agreements
	Under the Business Operation Agreements, the registered shareholders of VIEs and the VIEs may not enter into any transaction that could materially affect the assets, liabilities, interests or operations of the VIEs, without Qizhi Software's prior written consent. In addition, directors, general managers, financial controllers or other senior managers of VIEs must be Qizhi Software's nominees appointed by the registered shareholders of the VIEs. Each business operation agreement has a term of ten years and is renewable at Qizhi Software's sole discretion.
	Technology consulting and services agreements
	Under the Technology Consulting and Services Agreements, Qizhi Software agreed to provide the VIEs with technology support and consulting services. VIEs agreed to pay certain percentage of its revenue as service fees to Qizhi Software. The service fees are subject to adjustment by Qizhi Software. The agreements have a term of three to ten years unless terminated upon both parties' agreement. The agreement may be renewed upon Qizhi Software's approval and the renewed term will be based on agreement of both parties.
	Equity disposition agreements
	The agreements granted Qizhi Software or its designated person exclusive options to purchase, when and to the extent permitted under PRC law, any part or all of the equity interests in the VIEs. The exercise price for the options to purchase all of the equity interests is the minimum amount of consideration permissible under the then applicable PRC law. The agreements have an initial term of ten years and are renewable at Qizhi Software's sole discretion. Under the equity disposition agreements, the registered shareholders of the VIEs may sell the pledged shares to the Company at a nominal price to pay off the loans. The Company absorbs losses of the VIEs, and is exposed to the risk of losses from the operation of the VIEs.
	Loan agreements
	Under Loan Agreements between the Company and the registered shareholders of VIEs, the Company extended loans to the registered shareholders of VIEs for contributing registered capital to the VIEs in order to hold 100% of the equity interest in the VIEs. Each loan agreement has a term of ten years and is renewable upon both parties' agreement.
	Equity pledge agreements
	Under Qizhi Software's Equity Pledge Agreements with the VIEs and their respective registered shareholders, the registered shareholders of the VIEs pledged all of their respective equity interests in favor of Qizhi Software to secure VIEs' obligations under the Equity Disposition Agreements and Business Operation Agreements described above. If any of the VIEs breaches any of their respective contractual obligations under these agreements seriously, Qizhi Software, as pledgee, will be entitled to dispose the pledged equity interests. The registered shareholders of VIEs agreed not to dispose of, or otherwise create any new encumbrance on their respective equity interests in the VIEs, and not to approve the VIEs to merge with other entities or reorganize in any other forms, without Qizhi Software's prior written consent. Unless terminated at Qizhi Software's sole discretion, each equity pledge agreement has a term of ten years and is renewable at Qizhi Software's sole discretion, similar to the term of EquityDisposition Agreements and Business Operation Agreements.
	Power of attorney
	Each registered shareholder of VIEs, has executed a power of attorney appointing Qizhi Software to be his or her attorneys, and irrevocably authorizing Qizhi Software to vote on his or her behalf on all of the matters concerning the VIEs, that may require shareholders' approval. The term of power of attorney is ten years. The Power of Attorney can be renewed at Qizhi Software's sole discretion.
	Spousal consent
	Under the Spousal Consent letters, the spouse of each married registered shareholder of VIEs has signed a spousal consent letter, whereby the spouse agrees that (i) the equity interests of the VIEs owned by such shareholder will be disposed of only in accordance with the applicable EquityDisposition Agreement, Equity Pledge Agreement, Loan Agreement and other related agreements executed by the shareholder, (ii) such equity interests do not constitute communal property with such shareholder and (iii) the spouse irrevocably and unconditionally waives all rights and benefits with respect to such equity interests, including the right to sue in any court and under all applicable laws.
	As a result of the contractual arrangements described above, Qizhi Software has the power to direct the activities of the VIEs that most significantly affect the entity's economic performance, bears the economic risks and receives the economic benefits of the VIEs, and is the primary beneficiary of the VIEs. Therefore, the Company has consolidated the financial results of the VIEs and their subsidiaries in its consolidated financial statements since the later of the date of acquisition and incorporation.
	Risks in relation to the VIE structure
	The Company believes that Qizhi Software's contractual arrangements with the VIEs are in compliance with PRC law and are legally enforceable. However, uncertainties in the PRC legal system could limit the Company's ability to enforce the contractual arrangements. If the legal structure and contractual arrangements were found to be in violation of PRC laws and regulations, the PRC government could:
		·	revoke the Group's business and operating licenses
		·	require the Group to discontinue or restrict the Group's operations
		·	restrict the Group's right to collect revenues,
		·	block the Group's websites,
		·	require the Group to restructure the Group's operations,
		·	impose additional conditions or requirements with which the Group may not be able to comply
		·	impose restrictions on the Group's business operations or on the Group's customers or take other regulatory or enforcement actions against the Group that could be harmful to the Group's business.
	The Company's ability to conduct its business may be negatively affected if the PRC government were to carry out of any of the aforementioned actions. In addition, if any of our VIEs undergoes a voluntary or involuntary liquidation proceeding, its shareholders or unrelated third-party creditors may claim rights to some or all of its assets and the Company’s ability to operate its business may be negatively affected. As a result of aforementioned risks and uncertainties, the Company may not be able to consolidate the VIEs in its consolidated financial statements as it may lose the ability to exert effective control over the VIEs and their shareholders, and it may lose the ability to receive economic benefits from the VIEs.
	The shareholders of the VIEs are directors or officers of the Company. Most of them are also shareholders of the Company. Therefore they have no current interest in seeking to act contrary to the contractual arrangements. The interests of the VIEs' shareholders may differ from the interests of the Company as a whole. The Company cannot assure that when conflicts of interest arise, the shareholders will act in the best interests of the Company or that conflicts of interests will be resolved in the Company's favor. Currently, the Company does not have existing arrangements to address potential conflicts of interest the shareholders of the VIEs may encounter in their capacity as the beneficial owners and directors or officers of the VIEs, on the one hand, and as beneficial owners and directors or officers of the Company, on the other hand. The Company believes the shareholders of the VIEs will not act contrary to any of the contractual arrangements and the equity disposition agreements provide the Company with a mechanism to remove the shareholders as the beneficial shareholders of the VIEs should they act to the detriment of the Company. The Company relies on the VIEs' shareholders, as directors and officers of the Company, to fulfill their fiduciary duties and abide by laws of the PRC and Cayman Islands and act in the best interest of the Company. If the Company cannot resolve any conflicts of interest or disputes between the Company and the VIEs' shareholders, the Company would have to rely on legal proceedings, which could result in disruption of its business, and there is substantial uncertainty as to the outcome of any such legal proceedings.
	To further protect the investors' interest from any risk that the shareholders of the VIEs may act contrary to the contractual arrangements, the Company, through Qizhi Software, entered into irrevocable powers of attorney with the registered shareholders of the VIEs. Through these powers of attorney, the shareholders of the VIEs entrusted Qizhi Software as its proxy to exercise its rights as the shareholders of the VIEs with respect to an aggregate of 100% of the equity interests in the VIEs. The term of power of attorney is ten years. The power of attorney can be renewed at Qizhi Software's sole discretion.
	The following consolidated financial statement balances and amounts of the Group's VIEs and their subsidiaries were included in the accompanying consolidated financial statements after the elimination of intercompany balances and transactions between the offshore companies, WFOEs, VIEs and VIEs' subsidiaries in the Group:
			December 31,
			2013			2014
	Cash and cash equivalents		$	116,575		$	239,903
	Restricted cash			2,068			2,053
	Accounts receivable and other current assets			61,177			242,388
	Total current assets			179,820			484,344
	Property and equipment, net			91,861			138,345
	Acquired intangible assets, net			9,681			32,292
	Other noncurrent assets			37,778			301,070
	Total noncurrent assets			139,320			471,707
	Total assets			319,140			956,051
	Deferred revenue-current			30,717			44,869
	Accounts payable and other current liabilities			106,894			322,968
	Total current liabilities			137,611			367,837
	Total noncurrent liabilities			2,235			9,611
	Total liabilities		$	139,846		$	377,448
			Year ended December 31,
			2012			2013			2014
	Revenues		$	303,200		$	527,646		$	1,069,308
	Net income		$	150,408		$	263,514		$	451,191
			Year ended December 31,
		2012			2013			2014
Net cash provided by operating activities		$	75,983		$	129,175		$	439,351
Net cash used in investing activities			(50,951	)		(72,678	)		(305,996	)
Net cash provided by (used in) financing activities			36			1,970			(10,028	)
		$	25,068		$	58,467		$	123,327
As of December 31, 2012, 2013 and 2014, the balance of the amount payable by the VIEs and their subsidiaries to WOFEs related to the service fees was US$2.3 million, US$0.1 million and US$3.3 million, respectively and was eliminated upon consolidation.
The Group conducted substantially all of its Internet business through VIEs and the VIEs contributed an aggregate of 92.1%, 78.6% and 76.9% of the consolidated revenues for the years ended December 31, 2012, 2013 and 2014, respectively. The Group's operations not conducted through contractual arrangements with the VIEs primarily consist of its advertisement agency service and technology support service. As of December 31, 2013 and 2014, the VIEs accounted for an aggregate of 20.3% and 28.7%, respectively, of the consolidated total assets, and 17.2% and 17.2%, respectively, of the consolidated total liabilities. The assets not associated with the VIEs primarily consist of cash and cash equivalent, account receivables, property and equipment, and land use rights. The recognized and unrecognized revenue-producing assets that are held by the VIEs are primarily the following:
	·	Property and equipment
	·	Acquired intangible assets, such as domain names, licenses, trademarks, source code and non-compete agreements
	·	Other noncurrent assets, which mainly include long term royalty fees and license fees, long term rental deposits
	·	Self-developed intangible assets such as patents which are un-recognized at consolidated balance sheets
As of December 31, 2014, approximately 51.2% of the Group's employees that provide the Group's services are hired by the VIEs and their subsidiaries. The nominee shareholders of the VIEs and their subsidiaries have in the past received loans from the Company or WFOEs for capital contribution. There are no consolidated VIEs' assets that are collateral for the VIEs' obligations and can only be used to settle the VIEs' obligations. There are no creditors (or beneficial interest holders) of the VIEs that have recourse to the general credit of the Company or any of its consolidated subsidiaries. There are no terms in any arrangements, considering both explicit arrangements and implicit variable interests that require the Company or its subsidiaries to provide financial support to the VIEs. However, if the VIEs ever need financial support, the Company or its subsidiaries may, at its option and subject to statutory limits and restrictions, provide financial support to its VIEs through loans to the shareholder of the VIEs or entrustment loans to the VIEs.
Relevant PRC laws and regulations restrict the VIEs from transferring a portion of their net assets, equivalent to the balance of its statutory reserve and its share capital, to the Company in the form of loans and advances or cash dividends. Please refer to Note 23 for disclosure of restricted net assets.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies		2	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Basis of presentation
	The consolidated financial statements of the Group have been prepared in accordance with accounting principles generally accepted in the United States of America ("US GAAP").
	Basis of consolidation
	The consolidated financial statements of the Group include the financial statements of the Company, its wholly owned subsidiaries and VIEs and their subsidiaries. All inter-company transactions and balances have been eliminated upon consolidation.
	Use of estimates
	The preparation of the consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and the reported amounts of revenues and expenses in the consolidated financial statements and accompanying notes. Significant accounting estimates reflected in the Group's consolidated financial statements include allowance for doubtful accounts, purchase price allocation for business acquisitions, share-based compensation, valuation allowances for deferred tax assets, impairment assessment of long-term investments, impairment assessment of long-lived assets, useful lives of definite-lived intangible assets and other long-lived assets and impairment assessment of goodwill.
	Fair value measurements
	Fair value is 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 determine the fair value measurement for assets and liabilities required or permitted to be recorded at fair value, the Group considers the principle or most advantageous market in which it would transact and it considers assumptions that market participants would use when pricing the asset or liability.
	Authoritative literature provides a fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. The level in the hierarchy within which the fair value measurement in its entirety falls is based upon the lowest level of input that is significant to the fair value measurement as follows:
		·	Level 1-inputs are based upon unadjusted quoted prices for identical instruments traded in active markets.
		·	Level 2-inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
		·	Level 3-inputs are generally unobservable and typically reflect management's estimates of assumptions that market participants would use in pricing the asset or liability. The fair values are therefore determined using model-based techniques that include option pricing models, discounted cash flow models, and similar techniques.
	The Group measures certain assets, including long-term investments and intangible assets, at fair value on a nonrecurring basis when they are deemed to be impaired. The fair values of these investments and intangible assets are determined based on valuation techniques using the best information available, and may include management judgments, future performance projections, etc. An impairment charge to the long-term investments is recorded when the cost of the investment exceeds its fair value and this condition is determined to be other than-temporary, and impairment charge to the intangible assets is recorded when their carrying amounts may not be recoverable.
	Business combination
	Business combinations are recorded using the acquisition method of accounting. The consideration transferred is measured as the aggregate of the acquisition date fair values of the assets transferred, liabilities incurred, and equity instruments issued as well as the contingent considerations and all contractual contingencies as of the acquisition date. Transaction costs directly attributable to the acquisition are expensed as incurred. Identifiable assets and liabilities acquired or assumed are measured separately at their fair values as of the acquisition date, irrespective of the extent of any noncontrolling interests. The excess of (i) the total costs of acquisition, fair value of the noncontrolling interests and acquisition date fair value of any previously held equity interest in the acquiree over (ii) the fair value of the identifiable net assets of the acquiree is recorded as goodwill. If the cost of acquisition is less than the fair value of the net assets of the subsidiary acquired, the difference is recognized directly in the consolidated statements of operations.
	In a business combination achieved in stages, the Company re-measures the 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 the consolidated statements of operations.
	Cash and cash equivalents
	Cash and cash equivalents consist of cash on hand and term deposits, which are unrestricted as to withdrawal or use.
	Restricted cash
	Restricted cash mainly consists of the cash deposit used to secure for bank's acceptance bills in relation to payment for the construction of a building and for daily operation purchase, the cash balances deposits used to secure for application of an operation right, and cash deposits placed in certain escrow accounts for registration of new VIEs' wholly owned subsidiaries.
	Short-term investments
	All highly liquid investments with original maturities of greater than three months, but less than 12 months, are classified as short-term investments. Investments that are expected to be realized in cash during the next 12 months are also included in short-term investments. The Group’s short term investments are comprised of trading securities and available-for-sale investments.
	Trading securities
	The securities that are bought and held principally for the purpose of selling them in the near term are classified as trading securities. Unrealized holding gains and losses for trading securities are included in the consolidated statements of operations.
	Available-for-sale investments
	Investments not classified as either trading or as held-to-maturity are classified as available-for-sale investments. Available-for-sale investment is reported at fair value, with unrealized gains and losses recorded in accumulated other comprehensive income (loss) as a component of shareholders’ equity. Realized gains and losses and provision for decline in value judged to be other than temporary, if any, are recognized in the consolidated statements of operations.
	Accounts receivable and allowance for doubtful accounts
	Accounts receivable represents those receivables derived in the ordinary course of business. Allowance for doubtful accounts reflect the Group's best estimate of probable losses inherent in the accounts receivable balances. The Group regularly review allowances by considering factors such as historical experience, credit quality, the age of the accounts receivable balances and current economic conditions that may affect a customer's ability to pay.
	Fair value of financial instruments
	Financial instruments primarily consist of cash and cash equivalents, restricted cash, trading securities, short-term and long-term available-for-sale investments, accounts receivable, amounts due from related parties and accounts payable, amounts due to related parties, short-term loans and long-term debt. The carrying amounts of these financial instruments, except for long-term debt and long-term available-for-sale investments, approximate their fair values because of their generally short maturities.
	Property and equipment, net
	Property and equipment is carried at cost less accumulated depreciation and amortization. Depreciation and amortization are calculated on a straightline basis over the following estimated useful lives:
	Computer equipment and application software		3 – 6 years
	Building		44 – 60 years
	Office building related facility and machines		10 – 15 years
	Furniture and vehicles		3 – 10 years
	Leasehold improvements		lesser of the lease term or the
			estimated useful life of the assets
	Property and equipment that are purchased or constructed which require a period of time before the assets are ready for their intended use are accounted for as construction-in-progress. All the construction-in-progress has been converted into property and equipment during 2014 and there is nil construction-in-progress as of December 31, 2014. Construction-in-progress is recorded at acquisition cost, including installation costs. Construction-in-progress is transferred to specific property and equipment accounts and commences depreciation when these assets are ready for their intended use.
	Land use rights, net
	All land in the PRC is owned by the PRC government, which, according to the relevant PRC law, may grant the right to use the land for a specified period of time. Payment for acquiring land use rights are stated at cost less accumulated amortization and any recognized impairment loss. Amortization is provided on a straight-line basis over the term of the land use rights.
	Goodwill
	Goodwill represents the excess of the purchase consideration over the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed in business combinations. Goodwill is not amortized but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that it might be impaired. The Company first assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. In the qualitative assessment, the Company considers primary factors such as industry and market considerations, overall financial performance of the reporting unit, and other specific information related to the operations. Based on the qualitative assessment, if it is more likely than not that the fair value of each reporting unit is less than the carrying amount, the quantitative impairment test is performed.
	In performing the two-step quantitative impairment test, the first step compares the fair values of each reporting unit to its carrying amount, including goodwill. If the fair value of each reporting unit exceeds its carrying amount, goodwill is not considered to be impaired and the second step will not be required. If the carrying amount of a reporting unit exceeds its fair value, the second step compares the implied fair value of goodwill to the carrying value of a reporting unit’s goodwill. The implied fair value of goodwill is determined in a manner similar to accounting for a business combination with the allocation of the assessed fair value determined in the first step to the assets and liabilities of the reporting unit. The excess of the fair value of the reporting unit over the amounts assigned to the assets and liabilities is the implied fair value of goodwill. An impairment loss is recognized for any excess in the carrying value of goodwill over the implied fair value of goodwill. This allocation process is only performed for the purposes of evaluating goodwill impairment and does not result in an entry to adjust the value of any assets or liabilities. Application of a goodwill impairment test requires significant management judgment, including the identification of reporting units, assigning assets, liabilities and goodwill to reporting units, and determining the fair value of each reporting unit. The estimation of fair value of each reporting unit using a discounted cash flow methodology also requires significant judgments, including estimation of future cash flows, which is dependent on internal forecasts, estimation of the long-term rate of growth for the Group's business, estimation of the useful life over which cash flows will occur, and determination of the Group's weighted average cost of capital. The estimates used to calculate the fair value of a reporting unit change from year to year based on operating results and market conditions. Changes in these estimates and assumptions could materially affect the determination of fair value and goodwill impairment for the reporting unit.
	In 2014, the Group assessed the qualitative factors to determine it is not " more likely than not" that the fair value of each reporting unit is less than its respective carrying amount. The Group did not incur any impairment loss on goodwill for the years ended December 31, 2012, 2013 and 2014.
	Acquired intangible assets, net
	Acquired intangible assets are estimated by management based on the fair value of assets acquired. Identifiable intangible assets are carried at cost less accumulated amortization. Amortization of definite-lived intangible assets is computed using the straight-line method over the following estimated useful lives, which are as follows:
	Domain names		3 - 10 years
	Source code		5 - 8 years
	Technology		2 - 10 years
	Non-compete agreement		1 - 6 years
	Operating license		5 - 30 years
	Trademarks		3 - 10 years
	User base		0.5 - 1 year
	Customer relationship		3 years
	Distributor relationship		5 years
	Backlog		3 years
	Intangible assets with an indefinite useful life are not amortized and are tested for impairment annually or more frequently if events or changes in circumstances indicate that the asset might be impaired. Such impairment test is to compare the fair values of assets with their carrying amounts and an impairment loss is recognized if and when the carrying amounts exceed the fair values. The estimates of fair values of intangible assets not subject to amortization are determined using various discounted cash flow valuation methodologies. Significant assumptions are inherent in this process, including estimates of discount rates or market price. Discount rate assumptions are based on an assessment of the risk inherent in the respective intangible assets. Market prices are based on potential purchase quote from third party, if any.
	Impairment of long-lived assets other than goodwill
	The Company reviews long-lived assets with finite lives including identifiable intangible assets with determinable useful lives for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future net undiscounted cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Fair value is estimated based on various valuation techniques, including the discounted value of estimated future cash flows. The evaluation of asset impairment requires the Group to make assumptions about future cash flows over the life of the asset being evaluated. These assumptions require significant judgment and actual results may differ from assumed and estimated amounts.
	Long-term investments
	The Group’s long-term investments consist of cost method investments, equity method investments and available-for-sale investments.
	Cost-method investments
For equity investments that are not considered as equity securities that have readily determinable fair values and over which the Group neither has significant influence nor control through investment in common stock or in-substance common stock, the cost method is used. Investments in limited partnerships over whose operating and financing policies the Group has virtually no influence and with investment less than 5 percent are accounted for using the cost method.
Under the cost method, the Company carries the investment at cost and recognizes income to the extent of dividends received from the distribution of the equity investee’s post-acquisition profits.
Equity method investments
The Group applies the equity method to account for an equity investment, in common stock or in-substance common stock over which it has significant influence but does not own a majority equity interest or otherwise control. Significant influence is generally considered to exist when the Group has an ownership interest in the voting stock of the investee between 20% and 50%, and other factors, such as representation on the investee's board of directors, voting rights and the impact of commercial arrangements, are considered in determining whether the equity method of accounting is appropriate.
Under the equity method, the Group initially records its investment at cost and subsequently adjusts the carrying amount of the investment to recognize the Group’s proportionate share of each equity investee’s net income or loss into earnings after the date of investment. The Group records its share of the results of certain equity investees on a one quarter in arrears basis.
Available-for-sale investments
Available-for-sale investments represent investments in equity investees which are not intended to be realized in cash during the next 12 months are classified as long-term investments. They are measured with the same manner as short-term available-for-sale investments.
The Group continually reviews its investments in equity investees to determine whether a decline in fair value below the carrying value is other than temporary. The primary factors the Group considers in its determination are the length of time that the fair value of the investment is below the Group’s carrying value; the financial condition, operating performance and the prospects of the equity investee; and other Group specific information such as recent financing rounds. If the decline in fair value is deemed to be other than temporary, the carrying value of the equity investee is written down to fair value. The Group estimated the fair value of these investee companies based on discounted cash flow approach which requires significant judgments, including the estimation of future cash flows, which is dependent on internal forecasts, the estimation of long term growth rate of a company's business, the estimation of the useful life over which cash flows will occur, and the determination of the weighted average cost of capital.
Revenue recognition
The Group generates its revenue mainly through internet services. The Group recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, and collectability is reasonably assured.
Internet services revenue
Internet services revenue mainly includes online advertising and internet value-added services.
	-1	Online advertising
The Group offer marketing opportunities to customers by providing comprehensive online advertising service solutions, such as sponsored services (advertising services), on both of its PC and mobile platform products, such as 360 Personal Start-up Page, 360 Search and 360 Mobile Assistant. The Group charges fees to customers based on the effectiveness of its comprehensive advertising services, which is typically measured by active users, clicks, transactions and other actions originated from its platform products.  Additionally, fees are also affected by, among other factors, (i) the competitiveness of bidding for sponsored services and keywords by customers, with more intensive bidding typically leading to higher pricing and (ii) the vertical industries that customers operate in, which may result in different effectiveness and benefits of the Group's online advertising services to customers.
The Group generally collect fee of advertising services for customers on a cost over time period model or cost for performance model. For advertising contracts that are charged on the cost over a time period, the Group recognizes revenue ratably over the period the advertising is provided. For contracts that are charged on the cost for performance, the revenue is estimated by the Group based on its internal data, which is confirmed with the respective customers.
The Group engages in nonmonetary transactions such as to allow certain third parties to provide traffic on the non-monetization location of its platform products to show their brand or products in exchange for its brand promotion or more downloads of its platform or security products, and to allow certain third parties to bundle the Group's platform or security products with third parties' software products in exchange for more downloads of its platform or security products. The Group recognizes revenues and expenses at fair value from a nonmonetary transaction only if the fair value of the services exchanged in the transaction is determinable based on the entity's own historical practice of receiving cash, trading securities, or other consideration that is readily convertible to a known amount of cash for similar services from customers unrelated to the counterparty in the nonmonetary transaction. No such transactions were recognized in 2012, 2013 and 2014.
	-2	Internet value-added services
The Group's internet value-added services include offering games developed by third parties and providing other internet value-added services on the Group's platforms.
Games. The Group provides game services and generates revenues from selling in-game currency, which will later be used by game players to purchase in-game virtual items. The Group's game portfolio includes web games and mobile games. All of the games are developed by third-party game developers and can be accessed and played by game players directly through the Group's platform products. The Group primarily views the game developers to be its customers and considers its responsibility under its agreements with the game developers to be promotion of the game developers' games or assisting game developers to enhance game-playing experience. Sometimes, the Group gets exclusive rights in a certain region, that is, other platforms cannot provide the game without the Group’s permission.
The Group generally collects payments from game players in connection with the sale of in-game currencies and remits certain agreed-upon percentages of the proceeds to the game developers and records revenue net of remittances. Revenue from the sale of in-game currency is primarily recorded net of remittances to game developers and deferred until the estimated consumption date (i.e., the estimated date in-game currencies are consumed within the game if the Group only provides game promotion services, or the estimated date that virtual items are consumed if game enhancement service is also delivered). The in-game currencies are consumed typically within a short period of time after purchase which ranges from a few days to a few weeks depending on the game. Length of the consumption period is impacted by the Group’s portfolio mix of games and the monetization policy and marketing activity of each individual game as determined by game developers. The virtual items mainly consist of instant items and durable items. The life of instant items is less than one day, and the life of durable items is within months. An insignificant amount of revenue is recognized from durable items.
Purchases of in-game currency or virtual items are not refundable after they have been sold unless there is unused in-game currency at the time a game is discontinued. Typically, a game will only be discontinued when the monthly revenue generated by a game is insignificant. To date, the Group has never been required to pay cash refunds to game players or game developers as a result of the discontinuation of a game.
Other internet value-added services. The Group provides online lottery purchase services and serves as an agent for providing online distribution services and payment collection services on behalf of third-parties, such as collection payment for mobile charges, e-books and etc. The Group provides payment collection services mainly through third-party professional payment and settlement institutions. The Group generally charges commission as a percentage of the gross proceeds or collection amount, and the revenue is estimated by the Group based on its internal system, which is confirmed with the respective cooperators.
Other services
The Group offers enterprise information security products and related services to customers, such as firewalls, gateways and internet security monitoring system. Most of the Group’s revenue arrangements with customers is the sale of hardware products, bundled with software that is essential to the functionality of the hardware. The Group recognizes revenue for the sale of such hardware products after a sales agreement is signed, the price is fixed or determinable, products are delivered to customers, and collection of the resulting receivables is assured. Product is considered delivered to the customers once it has been shipped and title, risk of loss and rewards of ownership have been transferred.
Deferred revenue
Deferred revenue primarily includes cash received in advance from customers or end users and unrecognized license fee related to a license granted under a nonmonetary transaction, and deferred subsidy income. The unused cash balances remaining in customers or users' accounts are recorded as a liability. Deferred revenues related to prepayments from third party customers or end users will be recognized as revenue when all of the revenue recognition criteria are met, and deferred revenue related to license fee will be recognized as revenue based on the contract term.
Costs of revenues
Cost of revenues primarily consists of business tax, value added tax ("VAT") and related surcharges, payment collection costs, traffic acquisition costs, salaries and benefits, bandwidth costs, depreciation of equipment, cost of inventories, and revenue sharing to third party partners.
In July 2012, the Ministry of Finance and the State Administration of Taxation jointly issued a circular regarding the pilot collection of VAT in lieu of business tax in certain areas and industries in the PRC. Such VAT pilot program was to be phased in Beijing and Tianjin in September and December 2012, respectively. Starting from September 1, 2012, certain subsidiaries and VIEs of the Group became subject to VAT and related surcharges by various Chinese local tax authorities at rates ranging from 3.21% to 19.04% on revenue generated from providing services and enterprise information security products which were previously subject to business tax.
Business tax and VAT included in revenues and cost of revenues for the years ended December 31, 2012, 2013 and 2014 were $18,434, $39,909 and $80,514, respectively.
Product development expenses
The product development expenses primarily consist of costs associated with new product development and enhancement for existing products, such as salaries and benefits, including share-based compensation expenses, costs of bandwidth and utilities, license and technical service fees, and depreciation of equipment and amortization of acquired intangible assets.
Advertising costs
Advertising costs are expensed as incurred. The Group incurred advertising costs of $21,082, $62,301 and $231,198 for the years ended December 31, 2012, 2013 and 2014, respectively, which were recorded as a component of selling and marketing expenses in the accompanying consolidated statements of operations.
Operating leases
Leases where the rewards and risks of ownership of assets primarily remain with the lessor are accounted for as operating leases. The Group recognizes the operating lease expenses on a straight-line basis over the lease periods.
Subsidy income
Government subsidy is recorded as a liability in deferred revenue when received, and recognized as subsidy income Company complies with the conditions required for the subsidy. The Group recognized subsidy income of $2,570, $2,349 and $8,506 for the years ended December 31, 2012, 2013 and 2014, respectively.
Income taxes
The Group follows the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and tax basis of assets and liabilities using enacted tax rates that will be in effect for the period in which the differences are expected to reverse. The Group records a valuation allowance against the amount of deferred tax assets that it determines is not more-likely-than-not of being realized. The effect on deferred taxes of a change in tax rates is recognized in the consolidated statements of operations in the period that includes the enactment date.
The impact of an uncertain income tax position on the income tax return is recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant tax authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Interest and penalties on income taxes will be classified as a component of the provisions for income taxes.
Share-based compensation
Share-based compensation with employees is measured based on the grant date fair value of the equity instrument. The Group recognizes the compensation costs net of an estimated forfeiture rate using the straight-line method, over the requisite service period of the award, which is generally the vesting period of the award. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of share-based compensation expense to be recognized in future periods.
Share awards issued to nonemployees are measured at fair value at the earlier of the commitment date or the date the services is completed and recognized over the period the service is provided or as goods is received.
The Group uses the Black-Scholes or Binomial-Model option pricing model to measure the value of options granted to employees and nonemployees at each grant date or measurement date.
Net income per share
Basic net income per share is computed by dividing net income attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the year excluding any outstanding ordinary shares that are contingently refundable subject to the satisfaction of both the service and performance condition on the nonvested shares. Diluted net income per share reflects the potential dilution that could occur if securities or other contracts to issue ordinary shares were exercised or converted into ordinary shares.
The Company computes earnings per Class A and Class B ordinary shares using the two-class method. The unvested portions of nonvested shares are participating securities as all outstanding nonvested shares are entitled to nonforfeitable dividends that participate in undistributed earnings with ordinary shares. Since the nonvested shares are considered participating securities, the nonvested shares issued by the Company are required to apply the two-class method when computing basic earnings per share.
The Group has share options, nonvested shares and convertible senior notes which could potentially dilute basic earnings per share in the future. To calculate the number of shares for diluted net income per share, the effect of the share options is computed using the treasury stock method. The dilutive effect of the convertible senior notes is computed using as-if converted method.
Foreign currency translation
The functional and reporting currency of the Company and its subsidiaries located in HK is the United States dollar ("U.S. dollar"). The financial records of the Company's subsidiaries, VIEs and VIEs' subsidiaries located in the PRC are maintained in its local currency, the Renminbi ("RMB") which is the functional currency of these entities.
Monetary assets and liabilities denominated in currencies other than the functional currency are translated into the functional currency at the rates of exchange ruling at the balance sheet date. Transactions in currencies other than the functional currency during the year are converted into functional currency at the applicable rates of exchange prevailing when the transactions occurred. Transaction gains and losses are recognized in the consolidated statements of operations.
The Group's entities with functional currency of RMB translate their operating results and financial position into the U.S. dollar, the Company's reporting currency. Assets and liabilities are translated using the exchange rates in effect on the balance sheet date. Equity amounts are translated at historical exchange rates, and revenues, expenses, gains and losses are translated using the average rate for the year. Translation adjustments are reported as cumulative translation adjustments and are shown as a separate component of other comprehensive income in the consolidated statements of changes in equity and comprehensive income.
Comprehensive income
Comprehensive income of the Group includes the cumulative foreign currency translation adjustments, unrealized gains (losses) on available-for-sale investments and net income for the year. Comprehensive income is reported in the statements of comprehensive income.
Risks and uncertainties
The Group participates in a dynamic industry with rapid changes in regulations, technology trends, customer demand and competition and believes that changes in any of the following areas could have a material adverse effect on the Group's future financial position, results of operations, or cash flows: advances and trends in new technologies and industry standards; changes in certain strategic relationships or customer relationships; regulatory or other PRC related factors; risks associated with the Group's ability to attract and retain certain necessary employees to support its growth; risks associated with the Group's ability to keep and increase the user base; risks associated with the Group's growth strategies; risks associated with the Group’s ability to maintain and enhance brand and reputation and general risks associated with the internet security industry, and risks surrounding pending litigations.
Concentration of credit risk
Financial instruments that potentially expose the Group to concentrations of credit risk consist primarily of cash and accounts receivable. The Group places its cash with financial institutions with high-credit ratings and quality. The Group conducts credit evaluations of customers and generally does not require collateral or other security from their customers. The Group maintains reserves for potential credit losses.
Details of the customers that account for 10% or more of total revenues are as follow:
		Year ended December 31,
		2012			2013			2014
Customer
A			5	%		*-			*-
B			10	%		*-			*-
Details of the customers accounting for 10% or more of accounts receivable are as follows:
		December 31,
		2013			2014
Customer
B			32	%		*-
C			*-			14	%
“*” means less than 10%
Recently issued accounting standards adopted
In July 2013, the FASB issued an Accounting Standard Update ("ASU") which provides guidance on financial statement presentation of an unrecognized tax benefits when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists.  The FASB's objective in issuing this ASU is to eliminate diversity in practice resulting from a lack of guidance on this topic in current U.S. GAAP. The amendments in this ASU state that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except as follows. The adoption of this guidance did not have a significant effect on the Company's consolidated financial statements.
Recent accounting pronouncements not yet adopted
In April 2014, the FASB issued a new pronouncement which amends to change the criteria for reporting discontinued operations while enhancing disclosures in this area. It also addresses sources of confusion and inconsistent application related to financial reporting of discontinued operations guidance in U.S. GAAP.
Under the new guidance, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization's operations and financial results. Examples include a disposal of a major geographic area, a major line of business, or a major equity method investment.
In addition, the new guidance requires expanded disclosures about discontinued operations that will provide financial statement users with more information about the assets, liabilities, income, and expenses of discontinued operations.
The new guidance also requires disclosure of the pre-tax income attributable to a disposal of a significant part of an organization that does not qualify for discontinued operations reporting. This disclosure will provide users with information about the ongoing trends in a reporting organization's results from continuing operations. The amendments in the ASU are effective in the first quarter of 2015 for public organizations with calendar year ends. Early adoption is permitted. The Group is in the process of evaluating the impact of this pronouncement to its consolidated financial statements.
In May 2014, the FASB issued a new pronouncement which affects any entity using U.S. GAAP that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (e.g., insurance contracts or lease contracts). This ASU will supersede the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. This ASU also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition—Construction-Type and Production-Type Contracts. In addition, the existing requirements for the recognition of a gain or loss on the transfer of nonfinancial assets that are not in a contract with a customer (e.g., assets within the scope of Topic 360, Property, Plant, and Equipment, and intangible assets within the scope of Topic 350, Intangibles—Goodwill and Other) are amended to be consistent with the guidance on recognition and measurement (including the constraint on revenue) in this ASU.
The core principle of the guidance is that an entity should recognize revenue 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 that reporting period. Early application is not permitted.
An entity should apply the amendments in this ASU using one of the following two methods:
1. Retrospectively to each prior reporting period presented and the entity may elect any of the following practical expedients:
	·	For completed contracts, an entity need not restate contracts that begin and end within the same annual reporting period.
	·	For completed contracts that have variable consideration, an entity may use the transaction price at the date the contract was completed rather than estimating variable consideration amounts in the comparative reporting periods.
	·	For all reporting periods presented before the date of initial application, an entity need not disclose the amount of the transaction price allocated to remaining performance obligations and an explanation of when the entity expects to recognize that amount as revenue.
2. Retrospectively with the cumulative effect of initially applying this ASU recognized at the date of initial application. If an entity elects this transition method it also should provide the additional disclosures in reporting periods that include the date of initial application of:
The amount by which each financial statement line item is affected in the current reporting period by the application of this ASU as compared to the guidance that was in effect before the change.
An explanation of the reasons for significant changes.
The Group is in the process of evaluating the impact of this pronouncement to its 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 be 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.
Entities may apply the amendments in this ASU either: (a) prospectively to all awards granted or modified after the effective date; or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. If retrospective transition is adopted, the cumulative effect of applying this ASU as of the beginning of the earliest annual period presented in the financial statements should be recognized as an adjustment to the opening retained earnings balance at that date. In addition, if retrospective transition is adopted, an entity may use hindsight in measuring and recognizing the compensation cost. The adoption of this pronouncement will not have a significant impact on the Group’s consolidated financial statements.
The FASB has issued ASU 2015-03 which changes the presentation of debt issuance costs in financial statements. Under the ASU, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. The ASU specifies that “debt issuance costs related to a note shall be reported in the balance sheet as a direct deduction from the face amount of that note” and that “amortization of debt issuance costs also shall be reported as interest expense.” The ASU’s Basis for Conclusions observes that in practice, debt issuance costs incurred before the associated funding is received (i.e., before the issuance of the debt liability) are deferred on the balance sheet until that debt liability amount is recorded.
The amendments do not affect the current guidance on the recognition and measurement of debt issuance costs. For example, the costs of issuing convertible debt would not change the calculation of the intrinsic value of an embedded conversion option that represents a beneficial conversion feature under ASC 470-20-30-13. Thus, entities may still need to track debt issuance costs separately from a debt discount.
For public business entities, the amendments are effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. Early adoption of the amendments is permitted for financial statements that have not been previously issued.
The amendments should be applied on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Upon transition, an entity is required to comply with the applicable disclosures for a change in an accounting principle. These disclosures include the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted, and the effect of the change on the financial statement line items (i.e., debt issuance cost asset and the debt liability).
The Group is in the process of evaluating the impact of this pronouncement to its consolidated financial statements.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Acquisitions [Abstract]
Acquisitions		3	ACQUISITIONS
		-1	Acquisition of internet service business
	In January 2014, the Group acquired 100% equity interest of a game platform company with consideration of $66,146. The acquisition provided synergies with the existing business.
	The aggregate acquisition consideration consisted of (i) an initial consideration of $47,363 in cash, which was paid in 2014; and (ii) a contingent consideration of $20,000 in cash, subject to whether the amount of gross charges generated from the game platforms for the year ended December 31, 2014 meets specific targets stated in the acquisition agreement. The fair value of the contingent consideration was determined to be $18,783 at the acquisition date based on an estimation of the achievement of the operation goal. Fair value change in contingent consideration amounted $1,217 was recognized in consolidated statement of operations for the year ended December 31, 2014.
	The acquisition was recorded using the acquisition method of accounting and, accordingly, the acquired assets and liabilities were recorded at their fair market value at the date of acquisition. The total purchase price was allocated at the acquisition date as follows:
			US$
	Cash		$	14,730
	Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities			(18,238	)
	Intangible assets
	Non-compete agreement			5,438
	Domain name			3,008
	Technology			2,314
	User base			1,296
	Goodwill			60,612
	Deferred tax liability			(3,014	)
	Total		$	66,146
	The intangible assets valuations for the acquisitions described above were based on valuation analysis prepared by the management with the assistance of an independent third party valuation firm. The valuation analysis utilizes and considers generally accepted valuation methodologies such as the income, market and cost approaches. The Group has incorporated certain assumptions which include projected cash flows and replacement costs.
	The goodwill is mainly attributable to intangible assets that cannot be recognized separately as identifiable assets under US GAAP and comprise (a) the assembled work force and (b) the expected but unidentifiable business growth as a result of the synergy resulting from the acquisition.
	The operating results of this acquired business have been included in the Group's consolidated financial statements since the date of acquisition. It contributed net revenue of $138,919, and net loss of $7,504 to the Group's consolidated statement of operations for the year ended December 31, 2014.
	In July 2014, the Group sold a portion of this acquired business to one of its former shareholder for a total consideration of $12,000. The net carrying value of the disposed game platform business was $12,000 including goodwill of $9,951 allocated to the disposed business based on the relative fair values of the disposed business and the retained business at the disposal date. No gain or loss was recognized for this disposal.
		-2	Acquisition of internet service business
	In May 2014, the Group acquired 60% equity interest of an internet service company with consideration of $134,332 to expand its service scope in online advertising services. Among the total purchase consideration, $124,332 was paid upon the consummation of the acquisition and $10,000 was held back to satisfy losses, if any, for which the Group is entitled to indemnification from the selling shareholders. The holdback amount will be paid to the selling shareholders upon the first anniversary of the consummation of the acquisition.
	The acquisition was recorded using the acquisition method of accounting and, accordingly, the acquired assets and liabilities were recorded at their fair market value at the date of acquisition. The total purchase price was allocated at the acquisition date as follows:
			US$
	Cash		$	49,564
	Other net liabilities acquired, excluding intangible assets and the related deferred tax liabilities			(10,372	)
	Intangible assets
	Technology			9,377
	Non-compete agreement			3,259
	Customer relationship			1,204
	Goodwill			148,751
	Deferred tax liability			(2,076	)
	Non-controlling interest			(65,375	)
	Total		$	134,332
	The intangible assets valuations for the acquisitions described above were based on valuation analysis prepared by the management with the assistance of an independent third party valuation firm. The valuation analysis utilizes and considers generally accepted valuation methodologies such as the income, market and cost approaches. The Group has incorporated certain assumptions which include projected cash flows and replacement costs.
	The goodwill is mainly attributable to intangible assets that cannot be recognized separately as identifiable assets under US GAAP and comprise (a) the assembled work force and (b) the expected but unidentifiable business growth as a result of the synergy resulting from the acquisition.
	The operating results of this acquired business have been included in the Group's consolidated financial statements since the date of acquisition. It contributed net revenue of $25,946, and net loss of $5,829 to the Group's consolidated statement of operations for the years ended December 31, 2014.
		-3	Acquisition of enterprise information security business
	In October 2014, the Group acquired 75.1% equity interest of an enterprise information security company with a total consideration of $126,065 to expand its service offerings. The acquisition provided synergies with the existing business.
	The aggregate acquisition consideration consisted of (i) an initial consideration of $123,897 in cash, $89,938 was paid upon the consummation of the acquisition in 2014; and (ii) a contingent consideration of $2,168 in cash, subject to the net income generated from the enterprise information security business for the year ended December 31, 2018, December 31, 2019 and December 31, 2020 meeting certain specified targets stated in the acquisition agreement. The Group determines no fair value change in contingent consideration for the year ended December 31, 2014.
	The acquisition was recorded using the acquisition method of accounting and, accordingly, the acquired assets and liabilities were recorded at their fair market value at the date of acquisition. The total purchase price was allocated at the acquisition date as follows:
			US$
	Cash		$	50,292
	Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities			(22,324	)
	Intangible assets
	Distributor relationships			7,006
	Technology			3,436
	Operating license			1,808
	Customer relationships			1,303
	Backlog			1,254
	Trademarks			880
	Goodwill			115,757
	Deferred tax liability			(2,353	)
	Non-controlling interest			(30,994	)
	Total		$	126,065
	The intangible assets valuations for the acquisitions described above were based on valuation analysis prepared by the management with the assistance of an independent third party valuation firm. The valuation analysis utilizes and considers generally accepted valuation methodologies such as the income, market and cost approaches. The Group has incorporated certain assumptions which include projected cash flows and replacement costs.
	The goodwill is mainly attributable to intangible assets that cannot be recognized separately as identifiable assets under US GAAP and comprise (a) the assembled work force and (b) the expected but unidentifiable business growth as a result of the synergy resulting from the acquisition.
	The operating results of this acquired business have been included in the Group's consolidated financial statements since the date of acquisition. It contributed net revenue of $18,934, and net gain of $5,426 to the Group's consolidated statement of operations for the years ended December 31, 2014.
	Pro forma
	The following summarized unaudited pro forma results of operations for the year ended December 31, 2013 and 2014 assuming that all material acquisitions as stated in (1), (2) and (3) of this note during the two-year period ended December 31, 2014 occurred as of January 1, 2013. These pro forma results have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which actually would have resulted had the significant acquisitions occurred as of January 1, 2013, nor is it indicative of future operating results.
			Year ended December 31,
			2013			2014
			(Unaudited)			(Unaudited)
			US$			US$
Pro forma revenue			841,573			1,415,532
Pro forma net income (loss)			106,846			212,558
Pro forma earnings (loss) per ordinary share-basic			0.59			1.15
Pro forma earnings (loss) per ordinary share-diluted			0.55			1.08
	-4	Other acquisitions
Year 2014
	(i)	In May, 2014, the Group acquired 60% equity interest of an internet security business with a cash consideration of $1,092, which was fully paid in 2014. Goodwill of $122 was recognized from this acquisition.
	(ii)	In October, 2014, the Group acquired 100% equity interest of an internet security business with a cash consideration of $684, which was fully paid in 2014. Goodwill of $289 was recognized from this acquisition.
	(iii)	In November, 2014, the Group acquired 100% equity interest of an internet service business with a cash consideration of $1,302, which has not been paid as of December 31, 2014. Goodwill of $912 was recognized from this acquisition.
Year 2013
	(i)	In May, 2013, the Group acquired an internet service business with a cash consideration of $1,790, which was fully paid in 2013. Goodwill of $1,248 was recognized from this acquisition;
	(ii)	In May, 2013, the Group acquired 51% equity interest of a data center business with a cash consideration of $3,257, which was fully paid in 2013. Goodwill of $317 was recognized from this acquisition;
	(iii)	In July 2013, the Group acquired 51% equity interest of an overseas internet service company with consideration of $7,864 which was settled in the form of 204,466 ordinary shares of the Company, based upon the closing price of the Company's ADSs at the acquisition date, goodwill of $8,319 was recognized from this acquisition. One of the selling shareholders is the Chairman and Chief Executive Officer of the Company. The Company settled the consideration of $1,989 for 28.53% equity interest from the Chairman and Chief Executive Officer by issuance of 51,722 ordinary shares, equivalent to 34,481 ADSs, based upon the closing price of the Company's ADSs at the acquisition date.;
	(iv)	In September 2013, the Group acquired another 60% equity interest from the third-party shareholders for a cash consideration of $7,966, fully paid in 2013 and goodwill of $8,762 was resulted from the acquisition; and
	(v)	In November 2013, the Group acquired 51% equity interest of an internet service company by contributing $10,000 as registered capital to the acquiree, fully paid in 2013 and goodwill of $6,346 was resulted from the acquisition.
Pro forma
The following summarized unaudited pro forma results of operations for the year ended December 31, 2012 and 2013 assuming that all material acquisitions as stated in (4) of this note during the two-year period ended December 31, 2013 occurred as of January 1, 2012. These pro forma results have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which actually would have resulted had the significant acquisitions occurred as of January 1, 2012, nor is it indicative of future operating results.
		Year ended December 31,
		2012			2013
		(Unaudited)			(Unaudited)
			US$			US$
Pro forma revenue			336,774			676,414
Pro forma net income			43,857			95,937
Pro forma earnings (loss) per ordinary share-basic			0.25			0.53
Pro forma earnings (loss) per ordinary share-diluted			0.24			0.5
Year 2012
In September 2012, the Group acquired the remaining 65% equity interest in one of its equity method investees, a software development business with cash consideration of $312. $185 cash consideration was paid during 2012 and the remaining $127 was paid in 2013.

Accounts_Receivable

Accounts Receivable	12 Months Ended
	Dec. 31, 2014
Accounts Receivable [Abstract]
Accounts Receivable		4	ACCOUNTS RECEIVABLE
	Accounts receivable consists of the following:
			December 31,
			2013			2014
	Accounts receivable		$	54,743			156,697
	Allowance for doubtful accounts			(145	)		(2,410	)
	Accounts receivable, net		$	54,598		$	154,287
	Movement of allowance for doubtful accounts is as follows:
			December 31,
			2012			2013			2014
	Balance at beginning of year		$	68		$	213		$	145
	Addition in connection with business acquisition			-			-			2,020
	Charge to expense			154			157			349
	Write offs during the year			(10	)		(229	)		(74	)
	Exchange rate differences			1			4			(30	)
	Balance at end of year		$	213		$	145		$	2,410

Prepaid_Expenses_and_Other_Cur

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2014
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid Expenses and Other Current Assets		5	PREPAID EXPENSES AND OTHER CURRENT ASSETS
			December 31,
			2013		2014
	Prepayment for share repurchase (i)		$	-	$	104,201
	Prepaid expenses and other receivables			19,921		46,266
	Advance to suppliers			15,577		34,238
	Prepayment related to investments (ii)			12,325		29,704
	Interest receivable			3,219		5,314
	Receivables related to share options (iii)			29,496		1,473
	Prepaid expenses and other current assets		$	80,538	$	221,196
		(i)	The board of directors of the Group approved a $200 million share repurchase program in October 2014. As of December 31, 2014, the Company prepaid $104 million for the repurchase of shares. The Company completed the share repurchase program in February 2015.
		(ii)	The Group made several payments to establish new companies with other independent third parties. The prepayments will be recorded as long-term investments when the investees are legally established.
		(iii)	Amount represents the exercise cost to be received by the Group from a trading institution after the Group's employees exercised their stock options through such institution.

Investments

Investments

12 Months Ended

Dec. 31, 2014

Investments [Abstract]

Investments

6

INVESTMENTS

Short-term investments

The Group’s short-term investments consist of trading securities and available-for-sale investments. The carrying amount and fair value of the Group’s trading securities and short-term available-for-sale investments as of December 31, 2013 and 2014 were as follows:

As of December 31, 2013

Original

Gross

Gross

Provision

Fair

cost

unrealized

unrealized

for

value

gains

losses

decline

in value

Short-term investment:

Trading securities

179

168

(94

)

-

253

Available-for-sale securities:

Others

-

495

-

-

495

Short-term investment

674

168

(94

)

-

748

As of December 31, 2014

Original

Gross

Gross

Provision

Fair

cost

unrealized

unrealized

for

value

gains

losses

decline

in value

Short-term investment:

Trading securities

253

92

(172

)

-

173

Available-for-sale securities:

Listed equity securities

51,747

1,667

(9,856

)

—

43,558

Bank financial products

14,505

—

—

—

14,505

Others

500

—

—

—

500

Short-term investment

67,005

1,759

(10,028

)

—

58,736

The management of the Group determined that there was no impairment on such investment during the years ended December 31, 2012, 2013 and 2014.

Long-term investments

The Group’s long-term investments consist of cost method investments, equity method investments and available-for-sale investments.

Cost-method investments

The carrying amount of Company’s all cost method investments was $46,012 and $137,134 as of December 31, 2013 and 2014, respectively. The Group held less than 20% equity interest in its cost method investments except for the below investment:

In July 2012, the Group invested $482 in an entity engaged in internet service company, to purchase 26.51% of its equity interest. In January 2014, the Group made an additional investment for consideration of $17,445. As of December 31, 2014, the Group held 38.11% equity interest. The Group used the cost method to account for this investment though the Group held over 20% of its voting stock since the Group did not have the ability to exercise significant influence over the operating and financing activities of the investee.

The total impairment losses on cost method investments were $761, $867 and $578 during the years ended December 31, 2012, 2013 and 2014, respectively.

Equity-method investments

The carrying amount of Company’s equity method investments was $38,281 and $130,201 as of December 31, 2013 and 2014, respectively, with voting interests ranging from 10% to 65%. Details of the significant investments are as follows:

(i)

In November 2011, the Group acquired 30% equity interest of an internet security company through a nonmonetary transaction. In June 2012, the Group made an additional investment for an aggregate price of $2,140 in cash to avoid diluting in its series B financing. In December 2013, the Group made another additional investment for an aggregate price of $25,000 in cash in its series C financing. In December 2014, the Group made another additional investment for an aggregate price of $9,360 in cash in its series D financing. As of December 31, 2014, the Group held 40.8% equity interest with a carrying amount is $22,276.

(ii)

In December 2014, the Group purchased 40% of a hardware develop company’s equity interest for purchase price of $17,568.

The Group shared loss of $4,845, $2,747 and $18,906 from its equity method investments during the years end December 31, 2012, 2013 and 2014, respectively.

The total impairment losses on equity method investments were $1,541, $4,137 and $1,943 during the years ended December 31, 2012, 2013 and 2014, respectively.

Available-for-sale investments

The carrying amount and fair value of the Group’s available-for-sale investments were $nil and $47,644 as follows as of December 31, 2013 and 2014.

As of December 31, 2014

Original

Gross

Gross

Provision

Fair

cost

unrealized

unrealized

for

value

gains

losses

decline

in value

Long-term investment:

Available-for-sale securities:

Listed equity securities

57,335

9,988

(19,679

)

—

47,644

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 such as market condition for the investees’ industry and products and services. No impairment loss on available-for-sale investments was recognized for the years end December 31, 2012, 2013 and 2014.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Fair Value Measurements		7	FAIR VALUE MEASUREMENTS
	Measured on recurring basis
	The Group measured its financial assets including cash equivalents, trading securities and available-for-sale investment at fair value on a recurring basis as of December 31, 2013 and 2014.
	Cash equivalents represented term deposits that can be withdrawn at any time and are stated at fair value. Trading securities and available-for-sale equity investments included listed equity securities that are traded publicly in the open market. The Group classified such financial assets as investments within Level 1 of the fair value hierarchy because they are valued based on the quoted market price in an active market.
	Bank financial products are measured at costs which approximate their fair values in the consolidated balance sheets. The Group benchmarks the costs against fair values of comparable investments as of balance sheet date, and categorized all fair value measures of bank financial products as Level 2 of the fair value hierarchy because they are valued using directly or indirectly observable inputs in the market place.
	The contingent consideration related to business acquisition was classified within Level 3 of the fair value hierarchy because it is measured using significant unobservable inputs when determining its fair value by applying the income approach. The significant unobservable input was the discount rate of 13% and 14% which approximated to the industry weighted average cost of capital.
	The following table shows the fair value of the Group's financial assets and liabilities measured at recurring basis as of December 31, 2013 and 2014:
			As of December 31, 2013								As of December 31, 2014
			Fair Value Measurements at the Reporting Date Using								Fair Value Measurements at the Reporting Date Using
			Quoted prices in		Significant						Quoted prices in		Significant
			active markets		other		Significant				active markets		other		Significant
			for identical		observable		unobservable				for identical		observable		unobservable
			instruments		inputs		inputs		Total		instruments		inputs		inputs			Total
			(level 1)		(level 2)		(level 3)		balance		(level 1)		(level 2)		(level 3)			balance
	Cash equivalents-term deposits		$	683,994	$	-	$	-	$	683,994	$	1,129,833	$	-	$	-		$	1,129,833
	Short-term investments:
	Trading securities			253		-		-		253		173		-		-			173
	Available-for-sale investments
	Listed equity securities			-		-		-		-		43,558		-		-			43,558
	Bank financial products			-		-		-		-		-		14,505		-			14,505
	Others			-		495		-		495		-		500		-			500
	Long-term investments
	Listed equity securities			-		-		-		-		47,644		-		-			47,644
	Contingent consideration			-		-		-		-		-		-		(22,168	)		(22,168	)
	Total		$	684,247	$	495	$	-	$	684,742	$	1,221,208	$	15,005	$	(22,168	)	$	1,214,045
	The following is a reconciliation of the beginning and ending balances for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the years ended December 31, 2014, which only contains contingent consideration:
			Total
	Balance at December 31, 2013			-
	Addition in connection with business acquisition (Note 3(1)&(3))			20,951
	Increase in fair value			1,217
	Balance at December 31, 2014			22,168
	There was no such assets and liabilities existed during the years ended December 31, 2013.
	Measured on nonrecurring basis
	Long-term investments, goodwill and other intangible assets are measured at fair value on a nonrecurring basis and they are recorded at fair value only when impairment is recognized.
	The Group measured the fair value of the purchased intangible assets using the "cost," "income approach-excess earnings" and "with & without" valuation method.
	The Group measured the fair value of long term investments and acquired intangible assets using income approach based on which to recognize the impairment loss in respective years. These assets are considered as Level 3 assets because the Group used unobservable inputs to determine their fair values. The Group estimated the fair value of these investee companies and acquired intangible assets based on discounted cash flow approach which requires significant judgments, including the estimation of future cash flows, which is dependent on internal forecasts, the estimation of long term growth rate of a company’s business, the estimation of the useful life over which cash flows will occur, and the determination of the weighted average cost of capital.

Property_and_Equipment_Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2014
Property and Equipment, Net [Abstract]
Property and Equipment, Net		8	PROPERTY AND EQUIPMENT, NET
			December 31,
			2013		2014
	Computer equipment and application software		$	149,877	$	276,078
	Building			46,471		88,036
	Office building related facility and machines			14,022		27,988
	Furniture and vehicles			4,672		8,656
	Leasehold improvements			1,354		6,092
	Construction in Progress			5,469		-
				221,865		406,850
	Less: Accumulated depreciation and amortization			58,001		134,824
	Property and equipment, net		$	163,864	$	272,026
	Depreciation and amortization expenses for the years ended December 31, 2012, 2013 and 2014 were $14,768, $38,453 and $71,906, respectively.

Land_Use_Rights_Net

Land Use Rights, Net	12 Months Ended
	Dec. 31, 2014
Land Use Rights, Net [Abstract]
Land Use Rights, Net		9	LAND USE RIGHTS, NET
			December 31,
			2013		2014
	Land use rights		$	77,590	$	143,194
	Less: accumulated depreciation and amortization			1,892		4,087
	Land use rights, net		$	75,698	$	139,107
	Amortization expenses for land use rights totaled $140, $1,714 and $2,256 for the years ended December 31, 2012, 2013 and 2014.
	Future amortization expense will be $3,278 per year for each of the next five years through December 31, 2019.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2014
Goodwill [Abstract]
Goodwill		10	GOODWILL
			2013			2014
	Beginning balance		$	4,628		$	29,509
	Goodwill acquired in acquisitions of business			24,992			316,492
	Exchange rate differences			(111	)		(1,371	)
	Ending balance		$	29,509		$	344,630
	The Group assessed the qualitative factors to determine it is not more likely than not that the fair value of each reporting unit is less than its respective carrying amount. There was no impairment of goodwill during the years ended December 31, 2012, 2013 and 2014.

Acquired_Intangible_Assets_Net

Acquired Intangible Assets, Net	12 Months Ended
	Dec. 31, 2014
Acquired Intangible Assets, Net [Abstract]
Acquired Intangible Assets, Net		11	ACQUIRED INTANGIBLE ASSETS, NET
	The gross carrying amount, accumulated amortization and net carrying amount of the acquired intangible assets are as follows:
	Definite-lived intangible assets
			December 31,
			2013			2014
	Definite-lived
	Domain names		$	2,482		$	5,140
	Technology			12,013			28,043
	Non-compete agreement			3,985			13,026
	Customer relationship			2,973			5,110
	Distributor relationship			-			6,930
	Others			3,666			8,926
	Total acquired definite-lived intangible assets			25,119			67,175
	Less: Accumulated amortization
	Domain names			(859	)		(1,252	)
	Technology			(3,450	)		(7,627	)
	Non-compete agreement			(1,584	)		(4,426	)
	Customer relationship			(507	)		(1,552	)
	Distributor relationship			-			(347	)
	Others			(1,322	)		(3,225	)
	Less: Impairment loss
	Domain names			(424	)		(413	)
	Technology			(887	)		(859	)
	Others			(72	)		(70	)
	Acquired definite-lived intangible assets, net		$	16,014		$	47,404
	Amortization expenses for the years ended December 31, 2012, 2013 and 2014 were $1,689, $4,176 and $10,625 respectively. Amortization expenses for the years ending December 31, 2015, 2016, 2017, 2018 and 2019 and after are expected to be $12,571, $8,692, $7,688, $6,680 and $11,613 respectively.
	The Group performed impairment analysis and recognized an impairment loss of $1,151, $107 and $nil for the year ended December 31, 2012, 2013 and 2014, respectively for intangible assets with determinable useful lives.
	Indefinite-lived intangible assets
			December 31,
			2013			2014
	Indefinite-lived
	Domain names		$	371		$	2,937
	Trademarks and others			2,200			2,253
	Total acquired indefinite-lived intangible assets			2,571			5,190
	Less: Accumulated impairment loss
	Domain names			(288	)		(282	)
	Trademarks and others			(1,049	)		(1,023	)
	Accumulated impairment loss			(1,337	)		(1,305	)
	Acquired indefinite-lived intangible assets, net		$	1,234		$	3,885
	On December 31 of each year, the Group evaluated the remaining useful lives of the intangible assets with indefinite lives to determine whether events and circumstances continue to support an indefinite useful life. Based on impairment assessment, the Group recognized an impairment loss of $197, $841 and $nil for the years ended December 31, 2012, 2013 and 2014, respectively.

Accrued_Expenses_and_Other_Cur

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities [Abstract]
Accrued Expenses and Other Current Liabilities		12	ACCRUED EXPENSES AND OTHER CURRENT LIBILITIES
			December 31,
			2013		2014
	Payable related to investment and acquisition		$	365	$	64,545
	Payable for third-party service fee			30,017		56,772
	Accrued agent rebates			16,891		53,090
	Accrued payroll			19,217		37,540
	Other tax payable			12,094		21,097
	Deposits from advertising customers			10,060		19,747
	Payable for purchasing long-term assets			20,861		15,507
	Accrued interest expenses of convertible senior notes (see note 14)			4,808		10,062
	Other current liabilities			6,105		20,471
	Total		$	120,418	$	298,831

Deferred_Revenue

Deferred Revenue	12 Months Ended
	Dec. 31, 2014
Deferred Revenue [Abstract]
Deferred Revenue		13	DEFERRED REVENUE
	Deferred revenue primarily consists of customer advance and deferred income. Customer advance represents service fees prepaid by customers for which the relevant services have not been provided. Deferred income mainly includes deferred subsidy income and deferred reimbursement of ADS depositary service.
			December 31,
			2013		2014
	Deferred revenue - current
	Customers advance		$	33,979	$	52,548
	Deferred income			12,653		20,342
	Total deferred revenue - current		$	46,632	$	72,890
	Deferred revenue - noncurrent
	Customers advance		$	1,612	$	1,606
	Deferred income			1,932		675
	Total deferred revenue - noncurrent		$	3,544	$	2,281

Longterm_Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2014
Long-term Debt [Abstract]
Long-term Debt		14	LONG-TERM DEBT
	On September 5, 2013, the Company issued and sold publicly a tranche of unsecured senior notes with an aggregate principal amount of US$600 million which will mature on September 15, 2018 (the “2018 Notes”) at par.
	On August 6, 2014, the Company issued and sold publicly two tranches of unsecured senior notes:
		(i)	an aggregate principal amount of US$517.50 million which will mature on August 15, 2020 (the “2020 Notes”); and
		(ii)	an aggregate principal amount of US$517.50 million which will mature on August 15, 2021 (the “2021 Notes”).
	The 2018 Notes , 2020 Notes and 2021 Notes are collectively referred as “Notes”. The Notes will be the Company’s senior unsecured obligations and will rank (1) senior in right of payment to any of the Group's existing and future indebtedness that is expressly subordinated in right of payment to the Notes, (2) equal in right of payment to any of the Group's existing and future unsecured indebtedness that is not so subordinated, (3) junior in right of payment to any of the Group's secured indebtedness to the extent of the value of the assets securing such indebtedness and (4) structurally junior to all existing and future indebtedness and other obligations (including trade payables and lease obligations) incurred by the Group's subsidiaries.
	The Company has accounted for the Notes in accordance with ASC 470, as a single instrument as a long-term debt. The value of the Notes is measured by the cash received. As of December 31, 2014, $1,635,000 was accounted as the value of the Notes in long-term debt.
	Debt issuance costs were $ 30,780 and were recorded as deferred issuance costs, which were included in other noncurrent assets, are being amortized as interest expense, using the effective interest method, over the term of the Notes pursuant to ASC 835-30-35-2. The net proceeds the Company received from the issuance of the Notes were $587,850 and $1,016,370 for the year ended December 31, 2013 and 2014, respectively.
	The 2018 Notes bear interest at the rate of 2.50% per annum. Interests are payable semi-annually in arrears on and of each year, beginning on March 15, 2014. The 2020 Notes bear interest at the rate of 0.5% per annum and the 2021 Notes bear interest at the rate of 1.75% per annum. Interests are payable semi-annually in arrears on and of each year, beginning on February 15, 2015. At maturity, the Notes are payable at their principal amount plus accrued and unpaid interest thereon.
	The interest expense included in the consolidated statements of operations for the years ended December 31, 2014 and 2013, respectively, is as follows:
			For the year ended
			31-Dec-14
	Interest expense at an annual rate of 2.50%		$	15,981
	Interest expense at an annual rate of 0.50%		$	1,042
	Interest expense at an annual rate of 1.75%		$	3,614
	Amortization of debt issuance costs		$	3,373
	Total interest expense		$	24,010
			For the year ended
			31-Dec-13
	Interest expense at an annual rate of 2.50%		$	4,808
	Amortization of debt issuance costs		$	743
	Total interest expense		$	5,551
	The main terms of the Notes are summarized as follows:
	Redemption
	The 2018 Notes, 2020 Notes and 2021 Notes are not redeemable prior to the maturity date of September 15, 2018, August 15, 2020, and August 15, 2021, respectively, except as described below.
		-1	Non-contingent redemption option at the option of the holder
	The holders of the Notes (the "Holders") have an option to require the Company to repurchase for cash all or any portion of their 2018 Notes on September 15, 2016, 2020 Notes on August 15, 2017, and 2021 Notes on August 15, 2019. The repurchase price will equal 100% of the principal amount of the Notes to be repurchased plus accrued and unpaid interest, if any, to, but excluding, the repurchase date.
		-2	Contingent redemption option at the option of the holder
	If a fundamental change as stipulated in the Indenture dated September 5, 2013 in connection with the 2018 Notes, August 6, 2014 in connection with the 2020 Notes and 2021 Notes, occurs at any time prior to the maturity, the Holders have the option to require the Company to purchase for cash all or any portion of the Notes at a purchase price equal to 100% of the principal amount of the Notes to be purchased plus accrued and unpaid interest, if any, to, but excluding, the fundamental change purchase date.
	The Company believes that the likelihood of occurrence of events considered as a fundamental change is remote.
		-3	Redemption option at the option of the Company
	On or after September 15, 2016, August 15, 2017 and August 15, 2019, the Company may redeem any or all of the 2018 Notes, 2020 Notes, and 2021 Notes, respectively, in cash at the redemption price, provided that the last reported sale price of the Company's ADSs for 20 or more trading days in a period of 30 consecutive trading days ending within 10 trading days immediately prior to the date of the redemption notice exceeds 130% of the applicable conversion price in effect on each such trading day. The redemption price will equal 100% of the principal amount of the notes being redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date. Any notes redeemed by the Company will be paid for in cash.
	These embedded redemption features are considered clearly and closely related to the debt host pursuant to ASC 815-15-25 and does not meet the requirements for bifurcation.
	Conversion
	The Holders may convert their 2018 Notes, 2020 Notes, and 2021 Notes in integral multiples of $1 principle amount at an initial conversion rate of $110.96, $ 125.33, and $ 120.77 per ADS, respectively, at any time prior to the maturity date. Upon conversion of the Notes, the Company will deliver shares of the Company's ADS. The conversion rate is subject to adjustment in certain events, such as distribution of dividends and stock splits. In addition, upon a make-whole fundamental change as stipulated in the Indenture dated September 5, 2013 in connection with this 2018 Note, August 6, 2014 in connection with the 2020 Notes and 2021 Notes, the Company will, under certain circumstances, increase the applicable conversion rate for a holder that elects to convert its Notes in connection with such make-whole fundamental change.
	The conversion option meets the definition of a derivative. However, bifurcation of conversion option from the Notes is not required as the conversion option is considered indexed to the entity's own stock and classified in stockholders' equity.
	There was no beneficial conversion feature attribute to the Notes as the set conversion price for the Notes was greater than the fair value of the ordinary share price at date of issuance.
	The Holders have the option to convert upon a fundamental change, if Holders decide to convert in connection with a fundamental change; the number of shares issuable upon conversion will be increased. The Company will have to assess for the contingent beneficial conversion feature using a measurement date upon issuance of the Notes, upon occurrence of such adjustment.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Income Taxes		15	INCOME TAXES
	Cayman
	The Company is a tax-exempted company incorporated in the Cayman Islands.
	Hong Kong
	The Company's wholly-owned subsidiaries in Hong Kong are subject to the unified tax rate of 16.5% in Hong Kong for the years ended December 31, 2012, 2013 and 2014. Under the Hong Kong tax laws, these subsidiaries are exempted from income tax on its foreign-derived income and there are no withholding taxes in Hong Kong on remittance of dividends.
	Singapore
	The Company's wholly-owned subsidiary in Singapore, incorporated in 2013, is subject to the unified tax rate of 17% in Singapore for the year ended December 31, 2013 and 2014. There are no withholding taxes in Singapore on remittance of dividends.
	Japan
	The Company's majority-owned subsidiary in Japan, acquired in 2013, is subject to the unified tax rate of 25.5% plus 2.55% surcharge in Japan for the year ended December 31, 2013 and 2014. The company also needs to pay fixed amount local income tax to the local tax authorities on monthly basis, on the employee headcount and capital amount. The normal withholding tax rate is 20.42% in Japan on remittance of dividends and could be reduced to 10% under the tax treaty between Hong Kong and Japan.
	United States of America ("USA")
	The Company's wholly-owned subsidiary in USA, incorporated in 2013, is subject to the progressive tax rate from 15% to 39% for the federal income tax in the USA and 8.7% for the state income tax in Delaware for the year ended December 31, 2013 and 2014. The normal withholding tax rate is 30% in the USA on remittance of dividends.
	PRC
	The Group's PRC entities are subject to Enterprise Income Tax ("EIT") on the taxable income in accordance with the relevant PRC income tax laws.
	The Enterprise Income Tax Law ("the New EIT Law") became effective on January 1, 2008. The New EIT Law applies a uniform 25% enterprise income tax rate to both foreign invested enterprises and domestic enterprises except for certain entities that enjoy preferential tax rates, which are lower than the statutory rates, as described below.
	Under the New EIT Law and its implementing rules, an enterprise which qualifies as a "high and new technology enterprise" ("HNTE") is entitled to a tax rate of 15%. An enterprise which qualifies as a "Software Enterprise" 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. An enterprise which is approved to adopt the "deemed-profit method" can file its income tax by calculating as 2.5% of the gross revenues.
	Qizhi Software, Beijing Qihu and Beijing Star World were recognized as HNTE by relevant PRC government authorities, and were entitled to a reduced EIT rate of 15% for 2012, 2013 and 2014.
	Tianjin Qisi was recognized as Software Enterprise by relevant PRC government authorities in March 2011 and entitled to the preferential tax treatment of "2-year exemption plus 3-year half rate" commencing from its first profit-making year for EIT purposes. For the year ended December 31, 2012 and 2013, Tianjin Qisi enjoys the 2-year tax exemption. Tianjin Qisi was entitled to a preferential tax rate of 12.5% for the year ended December 31, 2014.
	Qifei Xiangyi was recognized as Software Enterprise by relevant PRC government authorities on Nov 11, 2013 and entitled to the preferential tax treatment of "2-year exemption plus 3-year half rate" commencing from its first profit-making year for EIT purposes. As a consequence, for the year ended December 31, 2013 and 2014, Qifei Xiangyi enjoys the 2-year tax exemption.
	Certain other PRC subsidiaries and VIEs are not subject to the unified tax rate of 25% as a result of adopting the "deemed-profit method" or the recognition as a qualified "Software Enterprise" or “HNTE”. And the other VIEs and VIEs' subsidiaries are all subject to the unified tax rate of 25%.
	Uncertainties exist with respect to how the current income tax law in the PRC applies to the Group's overall operations, and more specifically, with regard to tax residency status. The New EIT Law includes a provision specifying that legal entities organized outside of the PRC will be considered residents for Chinese Income tax purposes if the place of effective management or control is within the PRC. The implementation rules to the New EIT Law provide that non-resident legal entities will be considered PRC residents if substantial and overall management and control over the manufacturing and business operations, personnel, accounting, properties, etc., occurs within the PRC. Despite the present uncertainties resulting from the limited PRC tax guidance on the issue, the Group does not believe that the legal entities organized outside of the PRC within the Group should be treated as residents for EIT law purposes. If the PRC tax authorities subsequently determine that the Company, its subsidiaries, VIEs and VIEs' subsidiaries registered outside the PRC should be deemed a resident enterprise, the Company and its subsidiaries, VIEs and VIEs' subsidiaries registered outside the PRC will be subject to the PRC income tax at a rate of 25%.
	If the Company were to be non-resident for PRC tax purpose, dividends paid to it out of profits earned after January 1, 2008 would be subject to a withholding tax. In the case of dividends paid by PRC subsidiaries, the withholding tax would be 10%. Distributions made out of pre January 1, 2008 retained earnings will not be subject to the withholding tax. The Company's PRC entities historically have not declared or paid any dividends.
	Aggregate undistributed earnings of the Company's subsidiaries, VIEs and VIEs' subsidiaries located in the PRC that are available for distribution to the Company of $651,006 at December 31, 2014 are considered to be indefinitely reinvested, and accordingly, no provision has been made for the Chinese dividend withholding taxes that would be payable upon the distribution of those amounts to the Company. The Chinese tax authorities have also clarified that distributions made out of pre January 1, 2008 retained earnings will not be subject to the withholding tax.
	Detailed information about income tax of the Group's subsidiaries and VIEs is as below:
	The current and deferred portion of income tax expense included in the consolidated statements of operations is as follows:
			For the year ended December 31,
			2012			2013			2014
	Current income tax expense		$	12,062		$	22,382		$	69,693
	Deferred income tax (benefit) expense			(683	)		1,041			(18,268	)
	Total income tax expense		$	11,379		$	23,423		$	51,425
	The principal components of the deferred tax assets and liabilities are as follows:
			December 31,
			2013			2014
	Current deferred tax assets
	Accrued payroll		$	2,889		$	5,141
	Provision of allowance for doubtful accounts			92			478
	Deferred revenue-current			306			660
	Less: Valuation allowance			(158	)		(1,435	)
	Current deferred tax assets, net			3,129			4,844
	Noncurrent deferred tax assets
	Deferred revenue-noncurrent			383			339
	Intangible assets			266			953
	Fixed assets			66			100
	Subsidy income			231			270
	Net operating loss carry forwards			4,592			9,193
	Promotion fee			-			13,894
	Unrealized loss on available-for-sale investments			-			2,462
	Less: Valuation allowance			(4,592	)		(10,846	)
	Noncurrent deferred tax assets, net			946			16,365
	Noncurrent deferred tax liabilities
	Acquired intangible assets			2,676			8,159
	Unrealized gain on available-for-sale investments			-			357
	Noncurrent deferred tax liabilities		$	2,676		$	8,516
	The Company operates through its subsidiaries and VIEs and the valuation allowance is considered on each individual subsidiary and VIE basis. The subsidiaries and VIEs registered in the PRC have total net operating loss carry forwards of $50,874 as of December 31, 2014 which will expire on various dates between December 31, 2015 and December 31, 2019.
	Reconciliation between the income tax expense computed by applying the PRC tax rate to income before income tax and the actual provision for income tax is as follows:
			For the year ended December 31,
			2012			2013			2014
	Income before income tax expense		$	62,695		$	124,019		$	286,494
	PRC statutory income tax rate			25	%		25	%		25	%
	Income tax expense at the statutory income tax rate			15,674			31,005			71,624
	Permanent differences			870			1,663			5,506
	Effect of different income tax calculation method required by tax bureau			67			48			(5	)
	Effect of tax exempt status in Cayman Islands and other jurisdictions			12,217			30,241			24,701
	Effect of different income tax rate in Hong Kong			(25	)		168			273
	Effect of income tax holiday and preferential tax rates			(17,844	)		(43,460	)		(58,529	)
Changes in valuation allowance			420			3,758			7,855
Income tax expense		$	11,379		$	23,423		$	51,425
Certain consolidated entities of the Group enjoy tax holidays granted by the local tax authorities. Without the tax holidays, the Group's income tax expense would have increased by $17,844, $43,460 and $58,529 for the years ended December 31, 2012, 2013 and 2014, respectively. The impact of the tax holidays on basic net income per ordinary share was an increase of $0.10, $0.24 and $0.32 for the years ended December 31, 2012, 2013 and 2014, respectively.

Ordinary_Shares

Ordinary Shares	12 Months Ended
	Dec. 31, 2014
Ordinary Shares [Abstract]
Ordinary Shares		16	ORDINARY SHARES
	The Company's Memorandum and Articles of Association, as amended, authorizes the Company to issue 500,000,000 ordinary shares with a par value of $0.001 each as of December 31, 2012, 2013 and 2014, respectively.
	In January 2012, the Company's board of directors and shareholders approved a share repurchase program, which provided authorization to purchase up to $50 million worth of the Company's outstanding ADSs. In July 2012 and August 2012, the Company repurchased 900 and 8,796 ADSs, respectively, at a price of $14.50 and $14.31 through open-market transactions. In March 2013, the Company completed the legal process of registration for the repurchased stock.
	In December 2013, the Company issued 51,722 ordinary shares to a related party of the Company and 76,372 and 76,372 ordinary shares to each of the two selling shareholders , in connection with the Company's acquisition of 51% equity interest in an overseas internet service company (see note 3 (4)).
	In the years of 2012, 2013 and 2014, the Company issued 5,127,846, 4,543,902 and 4,525,410 ordinary shares for future delivery to the employees and nonemployees upon exercise of share options or grant of nonvested shares, respectively.
	As of December 31, 2014, there are 147,485,168 Class A ordinary shares and 45,931,163 Class B ordinary shares outstanding, par value $0.001 per share.
	The board of Company approved a $200 million share repurchase program in October 2014. As of December 31, 2014, the Company prepaid $104 million for repurchase of shares at market prices through open market transactions. The Company completed the share repurchase program in February 2015.

Net_Income_Per_Share

Net Income Per Share	12 Months Ended
	Dec. 31, 2014
Net Income Per Share [Abstract]
Net Income Per Share		17	NET INCOME PER SHARE
	The following table sets forth the computation of basic and diluted net income per share for the periods indicated:
			2012		2013		2014
	Net income attributable to Qihoo 360 Technology Co. Ltd			46,746		99,652		222,768
	Undistributed earnings allocated to participating unvested shares (i)			2,049		3,175		3,848
	Net income attributable to Class A and Class B ordinary shareholders for computing basic net income per ordinary share			44,697		96,477		218,920
	Net income attributable to nonvested shareholders for computing basic net income per participating unvested shares (i)			2,049		3,175		3,848
	Weighted average ordinary shares outstanding used in computing basic net income per Class A and Class B ordinary share			168,709,221		174,727,288		181,909,716
	Weighted average shares used in calculating net income per participating unvested share-basic			7,733,645		5,749,393		3,197,500
	Effect of dilutive securities:
	Plus incremental weighted average ordinary shares from assumed exercise of stock options and nonvested shares using the treasury stock method			7,180,369		12,560,169		12,384,156
	Weighted average ordinary shares outstanding used in computing diluted net income per Class A and Class B ordinary share (i)			183,623,235		193,036,850		197,491,372
	Net income per Class A and Class B ordinary share-basic			0.26		0.55		1.2
	Net income per participating unvested share-basic			0.26		0.55		1.2
	Net income per Class A and Class B ordinary share-diluted			0.25		0.52		1.13
		(i)	The net income attributable to Qihoo 360 Technology Co. Ltd. was allocated among Class A and Class B ordinary shares, and certain nonvested shares pro rata on the basis of their right to participate in dividends.
	For the year 2012, 2013 and 2014, 4,990,513, 533,054 and 244,797 share options were excluded as their effect was anti-dilutive, respectively.
	For the year 2012, 2013 and 2014, nil, 2,578,779 and 13,116,846 ordinary shares resulting from the assumed conversions of Convertible Senior Notes were excluded from the calculation of diluted net income per share as their effect was anti-dilutive.

Sharebased_Compensation

Share-based Compensation	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Share-based Compensation		18	SHARE-BASED COMPENSATION
	Share options
	On January 25, 2006, the Company adopted the 2006 Employee Share Option Plan (the "2006 Plan") for the granting of share options to employees and nonemployees to reward them for services to the Company and to provide incentives for future service. The share options expire ten years from the date of grant.
	On April 1, 2011, the Company adopted the 2011 Employee Share Incentive Plan (the "2011 Plan") for the granting of share options and nonvested shares (see note 18) to employees and nonemployees to reward them for services to the Company and to provide incentives for future service. The share options expire ten years from the date of grant.
	Option exercise
	The option shall be exercisable by giving notice in writing to the Company stating that the option is exercised and the number of shares in respect of which it is exercised. Any such notice must be accompanied by a remittance for the full amount of the exercise price for the shares in respect of which the notice is given.
	Vesting of options
	Under the 2006 Plan, the option will vest when the service conditions are met. In addition, according with the 2006 Plan, one of the exit events, described in "Termination of Option" below, shall happen. In accordance with the vesting schedules set out in the 2006 Plan, unless otherwise determined by the CEO of the Company, 1/4 of the options granted will be vested on each anniversary from the date of grant subject to the occurrence of one of the exit events.
	Under the 2011 Plan, the Plan administrator (compensation committee) has the authority to determine the schedule for vesting. The vast majority of share options granted under the 2011 Plan shall vest (i) 20 per cent of the aggregate number of options 12 months after the start of vesting period; (ii) 20 per cent of the aggregate number of options 24 months after the start of vesting period; (iii) 30 per cent of the aggregate number of options 36 months after the start of vesting period; and (iv) 30 per cent of the aggregate number of options 48 months after the start of vesting period.
	Termination of option
	Both under the 2006 and the 2011 Plan, the option may not be exercised until vested. Once vested, the option may be exercised in whole or any part, at any time. However, an option will be forfeited, if the grantee ceases to be an employee.
	Furthermore, in accordance with the 2006 Plan, an option will be forfeited, if the grantee ceases to be an employee prior to an exit, then (i) the portion of the option which has been otherwise vested and not exercised, and (ii) the portion of the options which has not been vested, will automatically lapse and expire.
	Exit means (i) a listing, (ii) a sale of all or substantially all of the issued share capital of the Company, (iii) a sale by the Company of all or substantially all of its assets, (iv) the passing of an effective resolution or the making of an order of a competent court for the winding up of the Company.
	Based on the terms above, the options will not actually vest until one of the exit events happens and the service conditions are met.
	Under the 2011 Plan, the Plan administrator (compensation committee) has the authority to terminate the option shall certain events happen.
	The fair value of the options granted is estimated on the date of grant using the Black-Scholes or Binomial-Model option-pricing model with the following assumptions used.
			Year ended December 31,
			2012		2013	2014
	Risk-free interest rate		2.83% - 3.35%		3.40% - 4.02%	3.96%~4.61%
	Expected life (years)		6.35		6.35	5.85~6.35
	Volatility		46.98% - 74%		46.04% - 46.68%	44.28%~46.02%
	Dividend yield		-		-	-
		-1	Volatility
	The volatility of the underlying ordinary shares during the life of the options was estimated based on the historical share price volatility of comparable companies over a period comparable to the expected term of the options.
		-2	Risk-free interest rate
	Risk-free interest rate was estimated based on the yield to maturity of China international government bonds with a maturity period close to the expected term of the options.
		-3	Expected term
	For the options granted to employees, as the Group did not have sufficient historical share option exercise experience, it estimated the expected term average based on a consideration of factors including contractual term and vesting period.
		-4	Dividend yield
	The dividend yield was estimated by the Group based on its expected dividend policy over the expected term of the options.
	The following table summarizes the option activity for the year ended December 31, 2014:
						Weighted average		Weighted average		Aggregate
						exercise price		remaining contractual		intrinsic value
			Number of options			per option		life (Years)		(in thousands)
	Outstanding at December 31, 2013			11,482,513		$	10.04		7.55		512,964
	Granted			258,500			45.35
	Exercised			(1,833,657	)		7.96
	Expired			(3,000	)		58.49
	Forfeited			(720,366	)		20.23
	Outstanding at December 31, 2014			9,183,990		$	10.57		6.61		257,557
	Vested and exercisable at December 31, 2014			4,913,833			7		6.09		153,647
	Vested and expect to vest at December 31, 2014			16,690,231			8.32		6.28		502,394
	The weighted-average grant-date fair value per option granted for the years ended December 31, 2012, 2013 and 2014 was $6.77, $13.19 and $32.61, respectively.
	The total intrinsic value of options exercised for the years ended December 31, 2012, 2013 and 2014 was $19,486, $138,364 and $98,112, 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.
	The Group recognized $26,997, $21,921 and $16,702 share-based compensation expense for the years ended December 31, 2012, 2013 and 2014, respectively.
	As of December 31, 2014, there was $18,875 unrecognized share-based compensation expense relating to share options. The expense is expected to be recognized over a weighted-average remaining vesting period of 0.73 years.
	Certain subsidiaries also have equity incentive plans. Total share-based compensation expenses recognized and unrecognized from such plans were insignificant, both individually and in aggregate, for all years presented.
	Nonvested shares
	On January 19, 2006, the Company's shareholder, Young Vision, the Series A shareholder and certain other parties entered into the Share Incentive Agreement, pursuant to which, Young Vision allocated a total of 18,086,101 ordinary shares of the Company to an equity incentive pool designed to award employees and consultants of the Group in accordance with the Employee Share Vesting Scheme (the "2006 Share Plan"), of which 9,951,000 shares were granted before January 1, 2008. In addition, in January 2010, the Company issued 3,517,544 nonvested shares in connection with certain 2009 acquisitions.
	In February 2011, Young Vision transferred 11,826,000 and 5,550,654 ordinary shares in the equity incentive pool to Sino Honor Limited ("Sino Honor") and Strengthen Goal Limited ("Strengthen Goal"), which are also companies owned by the Company's director and employee, respectively.
	The nonvested shares granted or vested in accordance with the 2006 Share Plan will, be held by Young Vision, Sino Honor and Strengthen Goal, and all rights (including without limitation, the voting rights and the right to receive the share certificates) attached to such shares will be exercised byYoung Vision, Sino Honor and Strengthen Goal at their sole and absolute discretion, except that the grantee shall have the right to all the monetary benefits deriving from the shares vested when the shares are disposed of in accordance with the 2006 Share Plan. Since the unvested nonvested shares are entitled to the same rights (including nonforfeitable dividend rights) and obligations as ordinary shares, these shares are considered participating securities.
	The nonvested shares granted under the 2006 Share Plan shall vest (i) 15 per cent of the aggregate number of shares 12 months after the start of vesting period; (ii) 20 per cent of the aggregate number of shares 24 months after the start of vesting period; (iii) 30 per cent of the aggregate number of shares so granted 36 months after the start of vesting period; and (iv) 35 per cent of the aggregate number of Shares 48 months after the start of vesting period.
	However, all nonvested shares to any grantee shall also be subject to the Company's rights to repurchase at an aggregate repurchase price of RMB1.00, if the grantee terminated his/her employment with the Group: (a) in all, on or before the second anniversary of the start of vesting period; (b) 50% of otherwise vested nonvested shares, after the second anniversary but before the fourth anniversary of the start of vesting period; or (c) no shares, after the fourth anniversary of the start of vesting period.
	Under the 2011 Plan, the nonvested shares granted shall vest based on service, or any other criteria selected by the Compensation Committee. If the grantee terminated his/her service ("Termination of Service") with the Group, the Group shall have the right to repurchase the unvested nonvested shares.
	Termination of Service means (i) As to a consultant, the time when she/he is terminated for any reason, (ii) As to a non-employee director, the time when non-employee director ceases to be a director for any reason, (iii) As to an employee, the time when the employee-employer relationship is terminated for any reason. However, all terminations shall exclude simultaneously commences or remains in employment or service with the Company, any subsidiaries or VIEs and VIEs' subsidiaries in others way.
	The following table summarizes information regarding the nonvested shares granted:
						Weighted average
						fair value per
			Number of			nonvested share
			nonvested shares			at the grant date
	Outstanding at December 31, 2013			10,070,794		$	15.44
	Granted			2,734,139			56.27
	Vested			(3,086,753	)		12.79
	Forfeited			(1,174,065	)		33.32
Outstanding at December 31, 2014			8,544,115		$	26.85
Vested and to be transferred to grantees at December 31, 2014			21,503,321
Vested and expect to vest at December 31, 2014			31,574,115
Included in the nonvested shares granted during 2013, there were 1,000,000 nonvested shares granted to the two co-founders of the Company to reward them for their outstanding performance in the past years. These nonvested shares vested immediately and the Company recognized $57,027 share based compensation expense as a result of such grant for the year ended December 31, 2013.
The fair value of the nonvested shares was determined by the closing sales price of the shares as quoted on the principal exchange or system. The total fair value of the nonvested shares vested for the years ended December 31, 2012, 2013 and 2014 was $8,361, $70,980 and $39,476, respectively.
The Group recognized $23,608, $99,166 and $77,364 share based compensation expense for the years ended December 31, 2012, 2013 and 2014 respectively.
As of December 31, 2014, total unrecognized compensation expense relating to the nonvested shares was $104,592. The expense is expected to be recognized over a weighted average period of 2.94 years using the graded vesting attribution method.

Related_Party_Balances_and_Tra

Related Party Balances and Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Balances and Transactions [Abstract]
Related Party Balances and Transactions		19	RELATED PARTY BALANCES AND TRANSACTIONS
	The amounts due from related parties mainly represent borrowings provided by the Group to investees in which the Group did not hold controlling interests, and amounts in connection with services provided by the Group to such investees, which arose in the ordinary course of business.
	The amounts due to related parties mainly represent unpaid revenue sharing in connection with game operation, which arose in the ordinary course of business.
	The transactions between the Group and related parties were insignificant, both individually and in aggregate.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
Commitments and Contingencies		20	COMMITMENTS AND CONTINGENCIES
		-1	Operating commitments
	The Group has future rental commitments related to facilities and offices under non-cancelable operating lease agreements, advertising agreements and fees commitment related to obtain exclusive rights of operating games on the Group's platform.
	Future minimum payments under those commitments as of December 31, 2014 were as follows:
	2015			27,437
	2016			6,460
	2017			4,061
	2018			2,070
	2019 and after			4,641
				44,669
	Rental expenses under operating leases for 2012, 2013 and 2014 were $5,967, $5,057 and $12,871, respectively.
		-2	Other commitments
	The Group has future commitment relates to interest payable in connection with the issuance of Notes (see Note 14).
	Assuming all debt was held to maturity, future maximum payments under those commitments as of December 31, 2014 were as follows:
	2015			26,644
	2016			26,644
	2017			26,644
	2018			22,269
	2019 and after			27,977
				130,178
		-3	Contingencies
	In October 2012, two affiliates of Baidu brought an unfair competitive practices and copyright infringement claim against the Group in the First Intermediate People's Court of Beijing, alleging that the Group breached the Robots Exclusion Protocol to access Baidu's content without authorization and seeking $16.1 million (RMB100.0 million) in damages. The court heard the case in October 2013 and ruled that the Group’s actions constituted unfair competition and awarded $0.1 million (RMB500,000) as damage to Baidu in August 2014. $0.1 million was accrued by the Group for such contingency. Baidu appealed in the Higher People’s Court of Beijing in August 2014. This case is currently pending.
	In February 2013, the Group brought a defamation claim against Shanghai Jingwen Culture Communication Co., Ltd. or Shanghai Jingwen, in the Xuhui District People's Court of Shanghai, alleging that Shanghai Jingwen published and distributed a series of false articles and reports against the Group on its website and electronic newspapers by maliciously accusing the level of safety and security of its products. The Group sought retraction of the defamatory statements, an apology from Shanghai Jingwen and $8.1 million (RMB50.0 million) in damages. In September 2014, the court ruled that Shanghai Jingwen’s actions constituted defamation and awarded $0.2 million (RMB1.5 million) and public apology to the Group. Shanghai Jingwen appealed to the First Intermediate People’s Court of Shanghai, and this case is currently pending.
	In October 2013, two affiliates of Sogou Inc. brought an unfair competitive practices claim against the Group in the Intermediate People’s Court of Xi’an, alleging that the Group used its software to change user default settings without their permission, including setting their default browser as 360 Safe Browser, which interfered with their use of Sogou’s browser. The claim sought cessation of the unfair competitive practices and $7.3 million (RMB45.5 million) in damages. This case was heard in July 2014 and is currently pending. In September 2013, the Group brought an unfair competitive practices claim against two affiliates of Sogou Inc., or Sogou, in the Second Intermediate People’s Court of Beijing, alleging that Sogou made defamatory statements on its public Weibo account and through online videos against the Group and seeking cessation of the unfair competitive practices, a retraction of the defamatory statements and $8.1 million (RMB50.0 million) in damages. This case was heard in May 2014 and the court ruled in December 2014 that the litigation shall be suspended, pending for the outcome of the unfair competition case brought by Sogou against the Group in Xi’an.
	In October 2013, two affiliates of Sogou Inc. brought an unfair competitive practices claim against the Group in the Second Intermediate People’s Court of Beijing, alleging that the Group’s 360 Safe Guard issued blocking notifications for other types of software, which negatively impacted their ability to run their business. The claim sought cessation of the unfair competitive practices and $8.1 million (RMB50.0 million) in damages. In January 2015, the court ruled that the Group’s actions constituted unfair competition and awarded $0.8 million (RMB5.1 million) as damage to Sogou. The Group appealed to the Higher People’s Court of Beijing and the case is currently pending. $0.8 million was accrued by the Group for such contingency based on the ruling of the court.
	In December 2014, Baidu brought an unfair competitive practice claim against the Group in the Intellectual Property Court of Beijing, alleging that the Group’s 360 Safe Guard issued pop-up notifications to block Baidu’s security software and made defamatory comments against Baidu in user’s name. The claim sought cessation of the unfair competitive practices and $1.6 million (RMB10.1 million) in damages. This case is currently pending.
	In December 2014, Baidu brought an unfair competitive practice claim against the Group in the Intellectual Property Court of Beijing, alleging that the Group’s search engine showed negative information when users are searching relevant key words to “Baidu” or “Li Yanhong”, which caused severe reputational damage to Baidu. The claim sought cessation of the unfair competitive practices and $1.6 million (RMB10.2 million) in damages. This case is currently pending.
	In December 2014, Baidu brought an unfair competitive practice claim against the Group in the Intellectual Property Court of Beijing, alleging that the Group set 10 key words in the pull-down menu of the search results prompt box of Baidu’s search engine and by clicking those key words the users would be redirected to the search results pages of 360 search engine. The claim sought cessation of the unfair competitive practices and $1.6 million (RMB10.0 million) in damages. This case is currently pending.
	Other than the aforementioned lawsuits, the Group is also a party to several legal proceedings or claims in China that the Group believes are immaterial.
	Based on information currently available, the Group cannot reasonably estimate the loss that is reasonably possible at this stage except for two of above cases. Therefore, $nil, $0.9 million and $0.9 million contingency loss were recognized in the consolidated financial statements as of December 31, 2012, 2013 and 2014, respectively.

Segments_and_Geographic_Inform

Segments and Geographic Information	12 Months Ended
	Dec. 31, 2014
Segments and Geographic Information [Abstract]
Segments and Geographic Information		21	SEGMENT AND GEOGRAPHIC INFORMATION
	The Group’s chief operating decision maker is the Chief Executive Officer and the President, who review consolidated results of operations prepared in accordance with U.S. GAAP when making decisions about allocating resources and assessing performance of the Group. The Group has operating segments: internet services and others. Others are insignificant.
	The Group does not allocate any assets to its operating segments as management does not believe that allocating these assets is useful in evaluating these segments' performance. Accordingly, the Group has not made disclosure of total assets by reportable segment.
			For the years ended December 31,
			2012			2013			2014
	Revenues:
	Internet services		$	328,882		$	671,088		$	1,370,695
	Others			150			-			19,965
				329,032			671,088			1,390,660
	Cost of revenues:
	Internet services			(32,762	)		(87,838	)		(297,645	)
	Others			(40	)		-			(7,817	)
				(32,802	)		(87,838	)		(305,462	)
	Gross profit:
	Internet services			296,120			583,250			1,073,050
	Others			110			-			12,148
				296,230			583,250			1,085,198
	Operating expenses:
	Product development			(156,269	)		(255,248	)		(406,250	)
	Selling and marketing			(58,178	)		(110,104	)		(333,701	)
	General and administrative			(35,643	)		(117,148	)		(94,260	)
	Total operating expenses			(250,090	)		(482,500	)		(834,211	)
	Subsidy income			2,570			2,349			8,506
	Income from operations		$	48,710		$	103,099		$	259,493
	Substantially all of the Group’s revenues for the three years ended December 31, 2012, 2013 and 2014 were generated from the PRC. Similarly, substantial all of the identifiable assets of the Group are located in the PRC. Accordingly, no geographical information is presented.

Mainland_China_Contribution_Pl

Mainland China Contribution Plan and Profit Appropriation	12 Months Ended
	Dec. 31, 2014
Contribution Plan and Profit Appropriation [Abstract]
Contribution Plan and Profit Appropriation		22	MAINLAND CHINA CONTRIBUTION PLAN AND PROFIT APPROPRIATION
	Full time employees of the Group in the mainland China participate in a government-mandated multi-employer defined contribution plan pursuant to which certain pension benefits, medical care, unemployment insurance, employee housing fund and other welfare benefits are provided to employees. Chinese labor regulations require the Group to accrue for these benefits based on certain percentages of the employees' salaries. The total provisions for such employee benefits were $18,125, $31,441 and $54,926 for the years ended December 31, 2012, 2013 and 2014, respectively.
	PRC legal restrictions permit payments of dividends by the Group's PRC entities only out of their retained earnings, if any, determined in accordance with PRC regulations. Prior to payment of dividends, pursuant to the laws applicable to the PRC Domestic Enterprises and PRC Foreign Investment Enterprises, the PRC entities must make appropriations from after-tax profit to non-distributable statutory reserve funds as determined by the Board of Directors of the Group. These reserve funds include the (1) general reserve, (2) enterprise expansion fund and (3) staff bonus and welfare fund. Subject to certain cumulative limits, the general reserve fund requires annual appropriations of not less than 10% of after-tax profit (as determined under accounting principles and financial regulations applicable to PRC enterprises at each year-end); the other two funds are at the Group's discretion. These reserve funds can only be used for specific purposes and are not distributable as cash dividends. The Group has made appropriation to these statutory reserve funds of $10,408, $12,074 and $21,284 for the years ended December 31, 2012, 2013 and 2014, respectively.

Restricted_Net_Assets

Restricted Net Assets	12 Months Ended
	Dec. 31, 2014
Restricted Net Assets [Abstract]
Restricted Net Assets		23	RESTRICTED NET ASSETS
	Relevant PRC statutory laws and regulations permit the payment of dividends by the Group's PRC subsidiaries, VIEs and VIEs' subsidiaries 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 be set aside as a reserve prior to the payment of dividends. As a result of these PRC laws and regulations, the Group's PRC subsidiaries, VIEs and VIEs' subsidiaries 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 balance of restricted net assets was $261,895and $474,595, of which $89,243 and $246,880 was attributed to the paid in capital and statutory reserves of the VIEs and VIEs' subsidiaries and $172,652, and $227,715 was attributed to the paid in capital and statutory reserves of the Company's PRC subsidiaries, as of December 31, 2013 and 2014, respectively. The PRC subsidiaries' accumulated profits may be distributed as dividends to the Company without the consent of a third party. The VIEs' revenues and accumulated profits may be transferred to Qizhi Software through contractual arrangements without the consent of a third party.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events		24	SUBSEQUENT EVENTS
	In December 2014, the Group entered into an agreement with Coolpad Group Limited, a leading smartphone manufacturer in China, to form a joint venture which will focus on designing, manufacturing, marketing and distributing smartphones and other mobile Internet devices. The Group acquired a 45% stake in the joint venture at a consideration of $409.05 million in cash. The transaction is expected to close in the second quarter of 2015.
	In October 2014, the Group's board of directors and shareholders approved another share repurchase program, which provided authorization to purchase up to $200 million worth of its outstanding ADSs.  This program was completed in February 2015.
	In March 2015, the Group authorized the repurchase of up to additional US$200 million of the Company's American Depositary Shares. The share repurchases are currently expected to be made through open market purchases or privately negotiated transactions as market conditions warrant, at prices the Company deems appropriate, and in accordance with the Securities and Exchange Commission requirements.

Additional_Information_Financi

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company	12 Months Ended
	Dec. 31, 2014
Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company [Abstract]
Condensed Financial Information of Parent Company		December 31,
		2013			2014
	ASSETS
	Current assets:
	Cash and cash equivalents	$	695,515		$	1,242,129
	Restricted cash		300			-
	Short-term investments		253			6,839
	Prepaid expenses and other current assets		3,206			111,872
	Amounts due from subsidiaries and VIEs		167,395			459,303
	Deferred tax assets - current		306			412
	Total current assets		866,975			1,820,555
	Acquired intangible assets, net		2,449			1,205
	Investments in subsidiaries and VIEs		449,893			799,123
	Long-term investments		17,139			45,211
	Other noncurrent assets		11,707			26,964
	Deferred tax assets - noncurrent		383			103
	TOTAL ASSETS	$	1,348,546		$	2,693,161
	LIABILITIES
	Current liabilities:
	Accrued expenses and other current liabilities		6,760			12,455
	Deferred revenue-current		1,150			1,539
	Amounts due to subsidiaries and VIEs		2,306			15,184
	Total current liabilities		10,216			29,178
	Deferred revenue-noncurrent		1,437			385
	Long-term debt		600,000			1,635,000
	TOTAL LIABILITIES	$	611,653		$	1,664,563
	EQUITY
	Qihoo 360 Technology Co. Ltd. shareholders' equity
	Class A ordinary shares ($0.001 par value; 378,000,000 and 378,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 134,123,218 and 147,485,168 shares issued and outstanding as of December 31, 2013 and 2014, respectively)		134			147
	Class B ordinary shares ($0.001 par value; 122,000,000 and 122,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 54,767,703 and 45,931,163 shares issued and outstanding as of December 31, 2013 and 2014, respectively)		55			46
	Treasury stock		(139	)		(139	)
	Additional paid-in capital		568,675			669,760
	Accumulated other comprehensive income (loss)		20,380			(11,772	)
	Retained earnings		147,788			370,556
	Total shareholders' equity		736,893			1,028,598
	TOTAL EQUITY		736,893			1,028,598
	TOTAL LIABILITIES AND EQUITY	$	1,348,546		$	2,693,161
		For the years ended December 31,
		2012			2013			2014
	Cost of revenues		4			-			-
	Operating expenses:
	Selling and marketing		21,289			15,519			15,666
	General and administrative		10,815			73,372			19,305
	Product development		21,782			38,211			59,375
	Total operating expenses		53,886			127,102			94,346
	Loss from operations		(53,890	)		(127,102	)		(94,346	)
	Interest income		4,702			6,341			20,264
	Interest expense		-			(5,551	)		(24,010	)
	Other income		1,277			1,197			1,447
	Exchange gain (loss)		412			5,100			(11,520	)
	(Loss) gain in connection with short-term investments		(52	)		327			10,230
	Gain in connection with long-term investments		-			413			-
	Loss before income tax expense and earnings from subsidiary and VIEs		(47,551	)		(119,275	)		(97,935	)
	Income in earnings of subsidiaries and VIEs		94,639			219,247			321,088
	Income before income tax expense		47,088			99,972			223,153
	Income tax expense		(342	)		(320	)		(385	)
	Net income attributable to Qihoo 360 Technology Co. Ltd.	$	46,746		$	99,652		$	222,768
		For the years ended December 31,
		2012			2013			2014
	Net income	$	46,746		$	99,652		$	222,768
	Other comprehensive income (loss), net of tax:
	Foreign currency translation adjustments		2,851			11,266			(42,342	)
	Unrealized loss on available-for-sale investments		-			-			10,190
	Other comprehensive income (loss)		2,851			11,266			(32,152	)
Comprehensive income		49,597			110,918			190,616
Add: Comprehensive loss attributable to noncontrolling interest		-			-			-
Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.	$	49,597		$	110,918		$	190,616
																		Total
																		Qihoo 360
													Accumulated			(Accumulated		Technology
										Additional			other			deficit)		Co. Ltd.
	Ordinary shares									paid-in			comprehensive			retained		shareholders'
	Shares			Amount			Treasury Stock			capital			income (loss)			earnings		equity
Balance as of January 1, 2012		179,029,251		$	179		$	-		$	363,021		$	6,263		$	1,390	$	370,853
Issuance of ordinary shares in connection with share-based compensation arrangements		3,512,394			3			-			-			-			-		3
Share-based compensation		-			-			-			50,605			-			-		50,605
Issuance of ordinary shares in connection with exercise of options		1,615,452			2			-			6,963			-			-		6,965
Disposal of noncontrolling interest in subsidiaries		-			-			-			73			-			-		73
Net income		-			-			-			-			-			46,746		46,746
Other comprehensive income		-			-			-			-			2,851			-		2,851
Balance as of December 31, 2012		184,157,097			184			-			420,662			9,114			48,136		478,096
Issuance of ordinary shares in connection with share-based compensation arrangements		561,517			1			-			-			-			-		1
Share repurchase		(14,544	)		-			(139	)		-			-			-		(139	)
Share-based compensation		-			-			-			121,087			-			-		121,087
Issuance of ordinary shares in connection with business acquisition		204,466			-			-			7,864			-			-		7,864
Issuance of ordinary shares in connection with exercise of options		3,982,385			4			-			19,067			-			-		19,071
Disposal of noncontrolling interest in subsidiaries		-			-			-			(5	)		-			-		(5	)
Net income		-			-			-			-			-			99,652		99,652
Other comprehensive income		-			-			-			-			11,266			-		11,266
Balance as of December 31, 2013		188,890,921			189			(139	)		568,675			20,380			147,788		736,893
Issuance of ordinary shares in connection with share-based compensation arrangements		2,691,753			2			-			-			-			-		2
Share-based compensation		-			-			-			90,392			-			-		90,392
Issuance of ordinary shares in connection with exercise of options		1,833,657			2			-			15,064			-			-		15,066
Acquisition of additional equity interests in subsidiaries		-			-			-			(4,371	)		-			-		(4,371	)
Net income		-			-			-			-			-			222,768		222,768
Other comprehensive loss		-			-			-			-			(32,152	)		-		(32,152	)
Balance as of December 31, 2014		193,416,331		$	193		$	(139	)	$	669,760		$	(11,772	)	$	370,556	$	1,028,598
	For the years ended December 31,
	2012			2013			2014
Cash flows from operating activities
Net income		46,746			99,652			222,768
Adjustments to reconcile net income to net cash provided by operating activities
Share-based compensation		50,605			121,087			89,686
Gain from investments in subsidiaries and VIEs		(94,639	)		(219,247	)		(321,089	)
Depreciation and amortization		582			1,476			1,243
Loss (gain) in connection with short-term investments		52			(327	)		(10,230	)
Gain in connection with long-term investments		-			(413	)		-
Prepaid expenses and other current assets		(2,307	)		463			(3,788	)
Deferred taxes		(178	)		(53	)		174
Other noncurrent assets		-			743			3,373
Accrued expenses and other current liabilities		149			5,488			5,694
Deferred revenue		700			215			(662	)
Amount due from/to subsidiaries and VIEs		(21,816	)		(128,738	)		(280,582	)
Net cash used in operating activities		(20,106	)		(119,654	)		(293,413	)
Cash flows from investing activities
(Increase) decrease in restricted cash		(300	)		-			300
Purchase of intangible assets		(1,500	)		(1,500	)		-
Purchase of short-term investments		-			(510	)		(30,025	)
Proceeds from sale of short-term investments		-			762			35,335
Capital contribution for long-term investments		(450	)		(15,760	)		(39,928	)
Dividends received from a cost method investee		-			413			-
Investment in subsidiaries		(1,200	)		-			(53,771	)
Net cash used in investing activities		(3,450	)		(16,595	)		(88,089	)
Cash flows from financing activities
Proceeds from issuance of Convertible Senior Notes (net of issuance costs of $12,150 and $18,630 in 2013 and 2014, respectively)		-			587,850			1,016,370
Proceeds from exercise of share options		2,089			23,678			15,947
Payment for share repurchase		(139	)		-			(104,201	)
Net cash provided by financing activities		1,950			611,528			928,116
Net (decrease) increase in cash and cash equivalents		(21,606	)		475,279			546,614
Cash and cash equivalents at beginning of year		241,842			220,236			695,515
Cash and cash equivalents at end of year		220,236			695,515			1,242,129

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
Basis of presentation	Basis of presentation
	The consolidated financial statements of the Group have been prepared in accordance with accounting principles generally accepted in the United States of America ("US GAAP").
Basis of consolidation	Basis of consolidation
	The consolidated financial statements of the Group include the financial statements of the Company, its wholly owned subsidiaries and VIEs and their subsidiaries. All inter-company transactions and balances have been eliminated upon consolidation.
Use of estimates	Use of estimates
	The preparation of the consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and the reported amounts of revenues and expenses in the consolidated financial statements and accompanying notes. Significant accounting estimates reflected in the Group's consolidated financial statements include allowance for doubtful accounts, purchase price allocation for business acquisitions, share-based compensation, valuation allowances for deferred tax assets, impairment assessment of long-term investments, impairment assessment of long-lived assets, useful lives of definite-lived intangible assets and other long-lived assets and impairment assessment of goodwill.
Fair value measurements	Fair value measurements
	Fair value is 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 determine the fair value measurement for assets and liabilities required or permitted to be recorded at fair value, the Group considers the principle or most advantageous market in which it would transact and it considers assumptions that market participants would use when pricing the asset or liability.
	Authoritative literature provides a fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. The level in the hierarchy within which the fair value measurement in its entirety falls is based upon the lowest level of input that is significant to the fair value measurement as follows:
		·	Level 1-inputs are based upon unadjusted quoted prices for identical instruments traded in active markets.
		·	Level 2-inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
		·	Level 3-inputs are generally unobservable and typically reflect management's estimates of assumptions that market participants would use in pricing the asset or liability. The fair values are therefore determined using model-based techniques that include option pricing models, discounted cash flow models, and similar techniques.
	The Group measures certain assets, including long-term investments and intangible assets, at fair value on a nonrecurring basis when they are deemed to be impaired. The fair values of these investments and intangible assets are determined based on valuation techniques using the best information available, and may include management judgments, future performance projections, etc. An impairment charge to the long-term investments is recorded when the cost of the investment exceeds its fair value and this condition is determined to be other than-temporary, and impairment charge to the intangible assets is recorded when their carrying amounts may not be recoverable.
Business combination	Business combination
	Business combinations are recorded using the acquisition method of accounting. The consideration transferred is measured as the aggregate of the acquisition date fair values of the assets transferred, liabilities incurred, and equity instruments issued as well as the contingent considerations and all contractual contingencies as of the acquisition date. Transaction costs directly attributable to the acquisition are expensed as incurred. Identifiable assets and liabilities acquired or assumed are measured separately at their fair values as of the acquisition date, irrespective of the extent of any noncontrolling interests. The excess of (i) the total costs of acquisition, fair value of the noncontrolling interests and acquisition date fair value of any previously held equity interest in the acquiree over (ii) the fair value of the identifiable net assets of the acquiree is recorded as goodwill. If the cost of acquisition is less than the fair value of the net assets of the subsidiary acquired, the difference is recognized directly in the consolidated statements of operations.
	In a business combination achieved in stages, the Company re-measures the 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 the consolidated statements of operations.
Cash and cash equivalents	Cash and cash equivalents
	Cash and cash equivalents consist of cash on hand and term deposits, which are unrestricted as to withdrawal or use.
Restricted cash	Restricted cash
	Restricted cash mainly consists of the cash deposit used to secure for bank's acceptance bills in relation to payment for the construction of a building and for daily operation purchase, the cash balances deposits used to secure for application of an operation right, and cash deposits placed in certain escrow accounts for registration of new VIEs' wholly owned subsidiaries.
Short-term investments	Short-term investments
	All highly liquid investments with original maturities of greater than three months, but less than 12 months, are classified as short-term investments. Investments that are expected to be realized in cash during the next 12 months are also included in short-term investments. The Group’s short term investments are comprised of trading securities and available-for-sale investments.
	Trading securities
	The securities that are bought and held principally for the purpose of selling them in the near term are classified as trading securities. Unrealized holding gains and losses for trading securities are included in the consolidated statements of operations.
	Available-for-sale investments
	Investments not classified as either trading or as held-to-maturity are classified as available-for-sale investments. Available-for-sale investment is reported at fair value, with unrealized gains and losses recorded in accumulated other comprehensive income (loss) as a component of shareholders’ equity. Realized gains and losses and provision for decline in value judged to be other than temporary, if any, are recognized in the consolidated statements of operations.
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts
	Accounts receivable represents those receivables derived in the ordinary course of business. Allowance for doubtful accounts reflect the Group's best estimate of probable losses inherent in the accounts receivable balances. The Group regularly review allowances by considering factors such as historical experience, credit quality, the age of the accounts receivable balances and current economic conditions that may affect a customer's ability to pay.
Fair value of financial instruments	Fair value of financial instruments
	Financial instruments primarily consist of cash and cash equivalents, restricted cash, trading securities, short-term and long-term available-for-sale investments, accounts receivable, amounts due from related parties and accounts payable, amounts due to related parties, short-term loans and long-term debt. The carrying amounts of these financial instruments, except for long-term debt and long-term available-for-sale investments, approximate their fair values because of their generally short maturities.
Property and equipment, net	Property and equipment, net
	Property and equipment is carried at cost less accumulated depreciation and amortization. Depreciation and amortization are calculated on a straightline basis over the following estimated useful lives:
	Computer equipment and application software		3 – 6 years
	Building		44 – 60 years
	Office building related facility and machines		10 – 15 years
	Furniture and vehicles		3 – 10 years
	Leasehold improvements		lesser of the lease term or the
			estimated useful life of the assets
	Property and equipment that are purchased or constructed which require a period of time before the assets are ready for their intended use are accounted for as construction-in-progress. All the construction-in-progress has been converted into property and equipment during 2014 and there is nil construction-in-progress as of December 31, 2014. Construction-in-progress is recorded at acquisition cost, including installation costs. Construction-in-progress is transferred to specific property and equipment accounts and commences depreciation when these assets are ready for their intended use.
Land use rights, net	Land use rights, net
	All land in the PRC is owned by the PRC government, which, according to the relevant PRC law, may grant the right to use the land for a specified period of time. Payment for acquiring land use rights are stated at cost less accumulated amortization and any recognized impairment loss. Amortization is provided on a straight-line basis over the term of the land use rights.
Goodwill	Goodwill
	Goodwill represents the excess of the purchase consideration over the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed in business combinations. Goodwill is not amortized but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that it might be impaired. The Company first assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. In the qualitative assessment, the Company considers primary factors such as industry and market considerations, overall financial performance of the reporting unit, and other specific information related to the operations. Based on the qualitative assessment, if it is more likely than not that the fair value of each reporting unit is less than the carrying amount, the quantitative impairment test is performed.
	In performing the two-step quantitative impairment test, the first step compares the fair values of each reporting unit to its carrying amount, including goodwill. If the fair value of each reporting unit exceeds its carrying amount, goodwill is not considered to be impaired and the second step will not be required. If the carrying amount of a reporting unit exceeds its fair value, the second step compares the implied fair value of goodwill to the carrying value of a reporting unit’s goodwill. The implied fair value of goodwill is determined in a manner similar to accounting for a business combination with the allocation of the assessed fair value determined in the first step to the assets and liabilities of the reporting unit. The excess of the fair value of the reporting unit over the amounts assigned to the assets and liabilities is the implied fair value of goodwill. An impairment loss is recognized for any excess in the carrying value of goodwill over the implied fair value of goodwill. This allocation process is only performed for the purposes of evaluating goodwill impairment and does not result in an entry to adjust the value of any assets or liabilities. Application of a goodwill impairment test requires significant management judgment, including the identification of reporting units, assigning assets, liabilities and goodwill to reporting units, and determining the fair value of each reporting unit. The estimation of fair value of each reporting unit using a discounted cash flow methodology also requires significant judgments, including estimation of future cash flows, which is dependent on internal forecasts, estimation of the long-term rate of growth for the Group's business, estimation of the useful life over which cash flows will occur, and determination of the Group's weighted average cost of capital. The estimates used to calculate the fair value of a reporting unit change from year to year based on operating results and market conditions. Changes in these estimates and assumptions could materially affect the determination of fair value and goodwill impairment for the reporting unit.
	In 2014, the Group assessed the qualitative factors to determine it is not " more likely than not" that the fair value of each reporting unit is less than its respective carrying amount. The Group did not incur any impairment loss on goodwill for the years ended December 31, 2012, 2013 and 2014.
Acquired intangible assets, net	Acquired intangible assets, net
	Acquired intangible assets are estimated by management based on the fair value of assets acquired. Identifiable intangible assets are carried at cost less accumulated amortization. Amortization of definite-lived intangible assets is computed using the straight-line method over the following estimated useful lives, which are as follows:
	Domain names		3 - 10 years
	Source code		5 - 8 years
	Technology		2 - 10 years
	Non-compete agreement		1 - 6 years
	Operating license		5 - 30 years
	Trademarks		3 - 10 years
	User base		0.5 - 1 year
	Customer relationship		3 years
	Distributor relationship		5 years
	Backlog		3 years
	Intangible assets with an indefinite useful life are not amortized and are tested for impairment annually or more frequently if events or changes in circumstances indicate that the asset might be impaired. Such impairment test is to compare the fair values of assets with their carrying amounts and an impairment loss is recognized if and when the carrying amounts exceed the fair values. The estimates of fair values of intangible assets not subject to amortization are determined using various discounted cash flow valuation methodologies. Significant assumptions are inherent in this process, including estimates of discount rates or market price. Discount rate assumptions are based on an assessment of the risk inherent in the respective intangible assets. Market prices are based on potential purchase quote from third party, if any.
Impairment of long-lived assets other than goodwill	Impairment of long-lived assets other than goodwill
	The Company reviews long-lived assets with finite lives including identifiable intangible assets with determinable useful lives for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future net undiscounted cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Fair value is estimated based on various valuation techniques, including the discounted value of estimated future cash flows. The evaluation of asset impairment requires the Group to make assumptions about future cash flows over the life of the asset being evaluated. These assumptions require significant judgment and actual results may differ from assumed and estimated amounts.
Long-term investments	Long-term investments
	The Group’s long-term investments consist of cost method investments, equity method investments and available-for-sale investments.
	Cost-method investments
	For equity investments that are not considered as equity securities that have readily determinable fair values and over which the Group neither has significant influence nor control through investment in common stock or in-substance common stock, the cost method is used. Investments in limited partnerships over whose operating and financing policies the Group has virtually no influence and with investment less than 5 percent are accounted for using the cost method.
	Under the cost method, the Company carries the investment at cost and recognizes income to the extent of dividends received from the distribution of the equity investee’s post-acquisition profits.
	Equity method investments
	The Group applies the equity method to account for an equity investment, in common stock or in-substance common stock over which it has significant influence but does not own a majority equity interest or otherwise control. Significant influence is generally considered to exist when the Group has an ownership interest in the voting stock of the investee between 20% and 50%, and other factors, such as representation on the investee's board of directors, voting rights and the impact of commercial arrangements, are considered in determining whether the equity method of accounting is appropriate.
	Under the equity method, the Group initially records its investment at cost and subsequently adjusts the carrying amount of the investment to recognize the Group’s proportionate share of each equity investee’s net income or loss into earnings after the date of investment. The Group records its share of the results of certain equity investees on a one quarter in arrears basis.
	Available-for-sale investments
	Available-for-sale investments represent investments in equity investees which are not intended to be realized in cash during the next 12 months are classified as long-term investments. They are measured with the same manner as short-term available-for-sale investments.
	The Group continually reviews its investments in equity investees to determine whether a decline in fair value below the carrying value is other than temporary. The primary factors the Group considers in its determination are the length of time that the fair value of the investment is below the Group’s carrying value; the financial condition, operating performance and the prospects of the equity investee; and other Group specific information such as recent financing rounds. If the decline in fair value is deemed to be other than temporary, the carrying value of the equity investee is written down to fair value. The Group estimated the fair value of these investee companies based on discounted cash flow approach which requires significant judgments, including the estimation of future cash flows, which is dependent on internal forecasts, the estimation of long term growth rate of a company's business, the estimation of the useful life over which cash flows will occur, and the determination of the weighted average cost of capital.
Revenue recognition	Revenue recognition
	The Group generates its revenue mainly through internet services. The Group recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, and collectability is reasonably assured.
	Internet services revenue
	Internet services revenue mainly includes online advertising and internet value-added services.
		-1	Online advertising
	The Group offer marketing opportunities to customers by providing comprehensive online advertising service solutions, such as sponsored services (advertising services), on both of its PC and mobile platform products, such as 360 Personal Start-up Page, 360 Search and 360 Mobile Assistant. The Group charges fees to customers based on the effectiveness of its comprehensive advertising services, which is typically measured by active users, clicks, transactions and other actions originated from its platform products.  Additionally, fees are also affected by, among other factors, (i) the competitiveness of bidding for sponsored services and keywords by customers, with more intensive bidding typically leading to higher pricing and (ii) the vertical industries that customers operate in, which may result in different effectiveness and benefits of the Group's online advertising services to customers.
	The Group generally collect fee of advertising services for customers on a cost over time period model or cost for performance model. For advertising contracts that are charged on the cost over a time period, the Group recognizes revenue ratably over the period the advertising is provided. For contracts that are charged on the cost for performance, the revenue is estimated by the Group based on its internal data, which is confirmed with the respective customers.
	The Group engages in nonmonetary transactions such as to allow certain third parties to provide traffic on the non-monetization location of its platform products to show their brand or products in exchange for its brand promotion or more downloads of its platform or security products, and to allow certain third parties to bundle the Group's platform or security products with third parties' software products in exchange for more downloads of its platform or security products. The Group recognizes revenues and expenses at fair value from a nonmonetary transaction only if the fair value of the services exchanged in the transaction is determinable based on the entity's own historical practice of receiving cash, trading securities, or other consideration that is readily convertible to a known amount of cash for similar services from customers unrelated to the counterparty in the nonmonetary transaction. No such transactions were recognized in 2012, 2013 and 2014.
		-2	Internet value-added services
	The Group's internet value-added services include offering games developed by third parties and providing other internet value-added services on the Group's platforms.
	Games. The Group provides game services and generates revenues from selling in-game currency, which will later be used by game players to purchase in-game virtual items. The Group's game portfolio includes web games and mobile games. All of the games are developed by third-party game developers and can be accessed and played by game players directly through the Group's platform products. The Group primarily views the game developers to be its customers and considers its responsibility under its agreements with the game developers to be promotion of the game developers' games or assisting game developers to enhance game-playing experience. Sometimes, the Group gets exclusive rights in a certain region, that is, other platforms cannot provide the game without the Group’s permission.
	The Group generally collects payments from game players in connection with the sale of in-game currencies and remits certain agreed-upon percentages of the proceeds to the game developers and records revenue net of remittances. Revenue from the sale of in-game currency is primarily recorded net of remittances to game developers and deferred until the estimated consumption date (i.e., the estimated date in-game currencies are consumed within the game if the Group only provides game promotion services, or the estimated date that virtual items are consumed if game enhancement service is also delivered). The in-game currencies are consumed typically within a short period of time after purchase which ranges from a few days to a few weeks depending on the game. Length of the consumption period is impacted by the Group’s portfolio mix of games and the monetization policy and marketing activity of each individual game as determined by game developers. The virtual items mainly consist of instant items and durable items. The life of instant items is less than one day, and the life of durable items is within months. An insignificant amount of revenue is recognized from durable items.
	Purchases of in-game currency or virtual items are not refundable after they have been sold unless there is unused in-game currency at the time a game is discontinued. Typically, a game will only be discontinued when the monthly revenue generated by a game is insignificant. To date, the Group has never been required to pay cash refunds to game players or game developers as a result of the discontinuation of a game.
	Other internet value-added services. The Group provides online lottery purchase services and serves as an agent for providing online distribution services and payment collection services on behalf of third-parties, such as collection payment for mobile charges, e-books and etc. The Group provides payment collection services mainly through third-party professional payment and settlement institutions. The Group generally charges commission as a percentage of the gross proceeds or collection amount, and the revenue is estimated by the Group based on its internal system, which is confirmed with the respective cooperators.
	Other services
	The Group offers enterprise information security products and related services to customers, such as firewalls, gateways and internet security monitoring system. Most of the Group’s revenue arrangements with customers is the sale of hardware products, bundled with software that is essential to the functionality of the hardware. The Group recognizes revenue for the sale of such hardware products after a sales agreement is signed, the price is fixed or determinable, products are delivered to customers, and collection of the resulting receivables is assured. Product is considered delivered to the customers once it has been shipped and title, risk of loss and rewards of ownership have been transferred.
Deferred revenue	Deferred revenue
	Deferred revenue primarily includes cash received in advance from customers or end users and unrecognized license fee related to a license granted under a nonmonetary transaction, and deferred subsidy income. The unused cash balances remaining in customers or users' accounts are recorded as a liability. Deferred revenues related to prepayments from third party customers or end users will be recognized as revenue when all of the revenue recognition criteria are met, and deferred revenue related to license fee will be recognized as revenue based on the contract term.
Costs of revenues	Costs of revenues
	Cost of revenues primarily consists of business tax, value added tax ("VAT") and related surcharges, payment collection costs, traffic acquisition costs, salaries and benefits, bandwidth costs, depreciation of equipment, cost of inventories, and revenue sharing to third party partners.
	In July 2012, the Ministry of Finance and the State Administration of Taxation jointly issued a circular regarding the pilot collection of VAT in lieu of business tax in certain areas and industries in the PRC. Such VAT pilot program was to be phased in Beijing and Tianjin in September and December 2012, respectively. Starting from September 1, 2012, certain subsidiaries and VIEs of the Group became subject to VAT and related surcharges by various Chinese local tax authorities at rates ranging from 3.21% to 19.04% on revenue generated from providing services and enterprise information security products which were previously subject to business tax.
	Business tax and VAT included in revenues and cost of revenues for the years ended December 31, 2012, 2013 and 2014 were $18,434, $39,909 and $80,514, respectively.
Product development expenses	Product development expenses
	The product development expenses primarily consist of costs associated with new product development and enhancement for existing products, such as salaries and benefits, including share-based compensation expenses, costs of bandwidth and utilities, license and technical service fees, and depreciation of equipment and amortization of acquired intangible assets.
Advertising costs	Advertising costs
	Advertising costs are expensed as incurred. The Group incurred advertising costs of $21,082, $62,301 and $231,198 for the years ended December 31, 2012, 2013 and 2014, respectively, which were recorded as a component of selling and marketing expenses in the accompanying consolidated statements of operations.
Operating leases	Operating leases
	Leases where the rewards and risks of ownership of assets primarily remain with the lessor are accounted for as operating leases. The Group recognizes the operating lease expenses on a straight-line basis over the lease periods.
Subsidy income	Subsidy income
	Government subsidy is recorded as a liability in deferred revenue when received, and recognized as subsidy income Company complies with the conditions required for the subsidy. The Group recognized subsidy income of $2,570, $2,349 and $8,506 for the years ended December 31, 2012, 2013 and 2014, respectively.
Income taxes	Income taxes
	The Group follows the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and tax basis of assets and liabilities using enacted tax rates that will be in effect for the period in which the differences are expected to reverse. The Group records a valuation allowance against the amount of deferred tax assets that it determines is not more-likely-than-not of being realized. The effect on deferred taxes of a change in tax rates is recognized in the consolidated statements of operations in the period that includes the enactment date.
	The impact of an uncertain income tax position on the income tax return is recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant tax authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Interest and penalties on income taxes will be classified as a component of the provisions for income taxes.
Share-based compensation	Share-based compensation
	Share-based compensation with employees is measured based on the grant date fair value of the equity instrument. The Group recognizes the compensation costs net of an estimated forfeiture rate using the straight-line method, over the requisite service period of the award, which is generally the vesting period of the award. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of share-based compensation expense to be recognized in future periods.
	Share awards issued to nonemployees are measured at fair value at the earlier of the commitment date or the date the services is completed and recognized over the period the service is provided or as goods is received.
	The Group uses the Black-Scholes or Binomial-Model option pricing model to measure the value of options granted to employees and nonemployees at each grant date or measurement date.
Net income per share	Net income per share
	Basic net income per share is computed by dividing net income attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the year excluding any outstanding ordinary shares that are contingently refundable subject to the satisfaction of both the service and performance condition on the nonvested shares. Diluted net income per share reflects the potential dilution that could occur if securities or other contracts to issue ordinary shares were exercised or converted into ordinary shares.
	The Company computes earnings per Class A and Class B ordinary shares using the two-class method. The unvested portions of nonvested shares are participating securities as all outstanding nonvested shares are entitled to nonforfeitable dividends that participate in undistributed earnings with ordinary shares. Since the nonvested shares are considered participating securities, the nonvested shares issued by the Company are required to apply the two-class method when computing basic earnings per share.
	The Group has share options, nonvested shares and convertible senior notes which could potentially dilute basic earnings per share in the future. To calculate the number of shares for diluted net income per share, the effect of the share options is computed using the treasury stock method. The dilutive effect of the convertible senior notes is computed using as-if converted method.
Foreign currency translation	Foreign currency translation
	The functional and reporting currency of the Company and its subsidiaries located in HK is the United States dollar ("U.S. dollar"). The financial records of the Company's subsidiaries, VIEs and VIEs' subsidiaries located in the PRC are maintained in its local currency, the Renminbi ("RMB") which is the functional currency of these entities.
	Monetary assets and liabilities denominated in currencies other than the functional currency are translated into the functional currency at the rates of exchange ruling at the balance sheet date. Transactions in currencies other than the functional currency during the year are converted into functional currency at the applicable rates of exchange prevailing when the transactions occurred. Transaction gains and losses are recognized in the consolidated statements of operations.
	The Group's entities with functional currency of RMB translate their operating results and financial position into the U.S. dollar, the Company's reporting currency. Assets and liabilities are translated using the exchange rates in effect on the balance sheet date. Equity amounts are translated at historical exchange rates, and revenues, expenses, gains and losses are translated using the average rate for the year. Translation adjustments are reported as cumulative translation adjustments and are shown as a separate component of other comprehensive income in the consolidated statements of changes in equity and comprehensive income.
Comprehensive income	Comprehensive income
	Comprehensive income of the Group includes the cumulative foreign currency translation adjustments, unrealized gains (losses) on available-for-sale investments and net income for the year. Comprehensive income is reported in the statements of comprehensive income.
Risks and uncertainties	Risks and uncertainties
	The Group participates in a dynamic industry with rapid changes in regulations, technology trends, customer demand and competition and believes that changes in any of the following areas could have a material adverse effect on the Group's future financial position, results of operations, or cash flows: advances and trends in new technologies and industry standards; changes in certain strategic relationships or customer relationships; regulatory or other PRC related factors; risks associated with the Group's ability to attract and retain certain necessary employees to support its growth; risks associated with the Group's ability to keep and increase the user base; risks associated with the Group's growth strategies; risks associated with the Group’s ability to maintain and enhance brand and reputation and general risks associated with the internet security industry, and risks surrounding pending litigations.
Concentration of credit risk	Concentration of credit risk
	Financial instruments that potentially expose the Group to concentrations of credit risk consist primarily of cash and accounts receivable. The Group places its cash with financial institutions with high-credit ratings and quality. The Group conducts credit evaluations of customers and generally does not require collateral or other security from their customers. The Group maintains reserves for potential credit losses.
	Details of the customers that account for 10% or more of total revenues are as follow:
			Year ended December 31,
			2012			2013			2014
	Customer
	A			5	%		*-			*-
	B			10	%		*-			*-
	Details of the customers accounting for 10% or more of accounts receivable are as follows:
			December 31,
			2013			2014
	Customer
	B			32	%		*-
	C			*-			14	%
	“*” means less than 10%
Recently issued accounting standards adopted	Recently issued accounting standards adopted
	In July 2013, the FASB issued an Accounting Standard Update ("ASU") which provides guidance on financial statement presentation of an unrecognized tax benefits when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists.  The FASB's objective in issuing this ASU is to eliminate diversity in practice resulting from a lack of guidance on this topic in current U.S. GAAP. The amendments in this ASU state that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except as follows. The adoption of this guidance did not have a significant effect on the Company's consolidated financial statements.
Recent accounting pronouncements not yet adopted	Recent accounting pronouncements not yet adopted
	In April 2014, the FASB issued a new pronouncement which amends to change the criteria for reporting discontinued operations while enhancing disclosures in this area. It also addresses sources of confusion and inconsistent application related to financial reporting of discontinued operations guidance in U.S. GAAP.
	Under the new guidance, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization's operations and financial results. Examples include a disposal of a major geographic area, a major line of business, or a major equity method investment.
	In addition, the new guidance requires expanded disclosures about discontinued operations that will provide financial statement users with more information about the assets, liabilities, income, and expenses of discontinued operations.
	The new guidance also requires disclosure of the pre-tax income attributable to a disposal of a significant part of an organization that does not qualify for discontinued operations reporting. This disclosure will provide users with information about the ongoing trends in a reporting organization's results from continuing operations. The amendments in the ASU are effective in the first quarter of 2015 for public organizations with calendar year ends. Early adoption is permitted. The Group is in the process of evaluating the impact of this pronouncement to its consolidated financial statements.
	In May 2014, the FASB issued a new pronouncement which affects any entity using U.S. GAAP that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets unless those contracts are within the scope of other standards (e.g., insurance contracts or lease contracts). This ASU will supersede the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. This ASU also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition—Construction-Type and Production-Type Contracts. In addition, the existing requirements for the recognition of a gain or loss on the transfer of nonfinancial assets that are not in a contract with a customer (e.g., assets within the scope of Topic 360, Property, Plant, and Equipment, and intangible assets within the scope of Topic 350, Intangibles—Goodwill and Other) are amended to be consistent with the guidance on recognition and measurement (including the constraint on revenue) in this ASU.
	The core principle of the guidance is that an entity should recognize revenue 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 that reporting period. Early application is not permitted.
	An entity should apply the amendments in this ASU using one of the following two methods:
	1. Retrospectively to each prior reporting period presented and the entity may elect any of the following practical expedients:
		·	For completed contracts, an entity need not restate contracts that begin and end within the same annual reporting period.
		·	For completed contracts that have variable consideration, an entity may use the transaction price at the date the contract was completed rather than estimating variable consideration amounts in the comparative reporting periods.
		·	For all reporting periods presented before the date of initial application, an entity need not disclose the amount of the transaction price allocated to remaining performance obligations and an explanation of when the entity expects to recognize that amount as revenue.
	2. Retrospectively with the cumulative effect of initially applying this ASU recognized at the date of initial application. If an entity elects this transition method it also should provide the additional disclosures in reporting periods that include the date of initial application of:
	The amount by which each financial statement line item is affected in the current reporting period by the application of this ASU as compared to the guidance that was in effect before the change.
	An explanation of the reasons for significant changes.
	The Group is in the process of evaluating the impact of this pronouncement to its 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 be 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.
	Entities may apply the amendments in this ASU either: (a) prospectively to all awards granted or modified after the effective date; or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. If retrospective transition is adopted, the cumulative effect of applying this ASU as of the beginning of the earliest annual period presented in the financial statements should be recognized as an adjustment to the opening retained earnings balance at that date. In addition, if retrospective transition is adopted, an entity may use hindsight in measuring and recognizing the compensation cost. The adoption of this pronouncement will not have a significant impact on the Group’s consolidated financial statements.
	The FASB has issued ASU 2015-03 which changes the presentation of debt issuance costs in financial statements. Under the ASU, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. The ASU specifies that “debt issuance costs related to a note shall be reported in the balance sheet as a direct deduction from the face amount of that note” and that “amortization of debt issuance costs also shall be reported as interest expense.” The ASU’s Basis for Conclusions observes that in practice, debt issuance costs incurred before the associated funding is received (i.e., before the issuance of the debt liability) are deferred on the balance sheet until that debt liability amount is recorded.
	The amendments do not affect the current guidance on the recognition and measurement of debt issuance costs. For example, the costs of issuing convertible debt would not change the calculation of the intrinsic value of an embedded conversion option that represents a beneficial conversion feature under ASC 470-20-30-13. Thus, entities may still need to track debt issuance costs separately from a debt discount.
	For public business entities, the amendments are effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. Early adoption of the amendments is permitted for financial statements that have not been previously issued.
	The amendments should be applied on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Upon transition, an entity is required to comply with the applicable disclosures for a change in an accounting principle. These disclosures include the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted, and the effect of the change on the financial statement line items (i.e., debt issuance cost asset and the debt liability).
	The Group is in the process of evaluating the impact of this pronouncement to its consolidated financial statements.

Organization_and_Principal_Act1

Organization and Principal Activities (Tables)	12 Months Ended
	Dec. 31, 2014
Organization and Principal Activities [Abstract]
Schedule of Variable Interest Entities		December 31,
		2013			2014
	Cash and cash equivalents	$	116,575		$	239,903
	Restricted cash		2,068			2,053
	Accounts receivable and other current assets		61,177			242,388
	Total current assets		179,820			484,344
	Property and equipment, net		91,861			138,345
	Acquired intangible assets, net		9,681			32,292
	Other noncurrent assets		37,778			301,070
	Total noncurrent assets		139,320			471,707
	Total assets		319,140			956,051
	Deferred revenue-current		30,717			44,869
	Accounts payable and other current liabilities		106,894			322,968
	Total current liabilities		137,611			367,837
	Total noncurrent liabilities		2,235			9,611
	Total liabilities	$	139,846		$	377,448
		Year ended December 31,
		2012			2013			2014
	Revenues	$	303,200		$	527,646		$	1,069,308
	Net income	$	150,408		$	263,514		$	451,191
		Year ended December 31,
		2012			2013			2014
	Net cash provided by operating activities	$	75,983		$	129,175		$	439,351
	Net cash used in investing activities		(50,951	)		(72,678	)		(305,996	)
	Net cash provided by (used in) financing activities		36			1,970			(10,028	)
		$	25,068		$	58,467		$	123,327

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
Property and Equipment, Estimated Useful Lives	Computer equipment and application software	3 – 6 years
	Building	44 – 60 years
	Office building related facility and machines	10 – 15 years
	Furniture and vehicles	3 – 10 years
	Leasehold improvements	lesser of the lease term or the
		estimated useful life of the assets
Acquired Intangible Assets, Estimated Useful Lives	Domain names	3 - 10 years
	Source code	5 - 8 years
	Technology	2 - 10 years
	Non-compete agreement	1 - 6 years
	Operating license	5 - 30 years
	Trademarks	3 - 10 years
	User base	0.5 - 1 year
	Customer relationship	3 years
	Distributor relationship	5 years
	Backlog	3 years
Total revenue [Member] | Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration of Credit Risk		Year ended December 31,
		2012			2013			2014
	Customer
	A		5	%		*-			*-
	B		10	%		*-			*-
	“*” means less than 10%
Accounts receivable [Member] | Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration of Credit Risk		December 31,
		2013			2014
	Customer
	B		32	%		*-
	C		*-			14	%
	“*” means less than 10%

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2014
Internet service company acquired in January 2014 [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation
		US$
	Cash	$	14,730
	Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities		(18,238	)
	Intangible assets
	Non-compete agreement		5,438
	Domain name		3,008
	Technology		2,314
	User base		1,296
	Goodwill		60,612
	Deferred tax liability		(3,014	)
	Total	$	66,146
Internet service company acquired in May 2014 [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation
		US$
	Cash	$	49,564
	Other net liabilities acquired, excluding intangible assets and the related deferred tax liabilities		(10,372	)
	Intangible assets
	Technology		9,377
	Non-compete agreement		3,259
	Customer relationship		1,204
	Goodwill		148,751
	Deferred tax liability		(2,076	)
	Non-controlling interest		(65,375	)
	Total	$	134,332
Enterprise information security business acquired in October 2014 [Member]
Business Acquisition [Line Items]
Business Acquisition, Purchase Price Allocation		US$
	Cash	$	50,292
	Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities		(22,324	)
	Intangible assets
	Distributor relationships		7,006
	Technology		3,436
	Operating license		1,808
	Customer relationships		1,303
	Backlog		1,254
	Trademarks		880
	Goodwill		115,757
	Deferred tax liability		(2,353	)
	Non-controlling interest		(30,994	)
	Total	$	126,065
Aggregated individually material acquirees acquired in 2014 [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information		Year ended December 31,
		2013			2014
		(Unaudited)			(Unaudited)
		US$			US$
	Pro forma revenue		841,573			1,415,532
	Pro forma net income (loss)		106,846			212,558
	Pro forma earnings (loss) per ordinary share-basic		0.59			1.15
	Pro forma earnings (loss) per ordinary share-diluted		0.55			1.08
Aggregated individually material acquirees acquired in 2013 [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information		Year ended December 31,
		2012			2013
		(Unaudited)			(Unaudited)
			US$			US$
	Pro forma revenue		336,774			676,414
	Pro forma net income		43,857			95,937
	Pro forma earnings (loss) per ordinary share-basic		0.25			0.53
	Pro forma earnings (loss) per ordinary share-diluted		0.24			0.5

Accounts_Receivable_Tables

Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2014
Accounts Receivable [Abstract]
Schedule of Accounts Receivable		December 31,
		2013			2014
	Accounts receivable	$	54,743			156,697
	Allowance for doubtful accounts		(145	)		(2,410	)
	Accounts receivable, net	$	54,598		$	154,287
Movement of Allowance for Doubtful Accounts		December 31,
		2012			2013			2014
	Balance at beginning of year	$	68		$	213		$	145
	Addition in connection with business acquisition		-			-			2,020
	Charge to expense		154			157			349
	Write offs during the year		(10	)		(229	)		(74	)
	Exchange rate differences		1			4			(30	)
	Balance at end of year	$	213		$	145		$	2,410

Prepaid_Expenses_and_Other_Cur1

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Prepaid Expenses and Other Current Assets [Abstract]
Schedule of Prepaid Expenses and Other Current Assets			December 31,
			2013		2014
	Prepayment for share repurchase (i)		$	-	$	104,201
	Prepaid expenses and other receivables			19,921		46,266
	Advance to suppliers			15,577		34,238
	Prepayment related to investments (ii)			12,325		29,704
	Interest receivable			3,219		5,314
	Receivables related to share options (iii)			29,496		1,473
	Prepaid expenses and other current assets		$	80,538	$	221,196
		(i)	The board of directors of the Group approved a $200 million share repurchase program in October 2014. As of December 31, 2014, the Company prepaid $104 million for the repurchase of shares. The Company completed the share repurchase program in February 2015.
		(ii)	The Group made several payments to establish new companies with other independent third parties. The prepayments will be recorded as long-term investments when the investees are legally established.
		(iii)	Amount represents the exercise cost to be received by the Group from a trading institution after the Group's employees exercised their stock options through such institution.

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Short-term Investments		As of December 31, 2013
		Original		Gross		Gross			Provision		Fair
		cost		unrealized		unrealized			for		value
				gains		losses			decline
									in value
	Short-term investment:
	Trading securities		179		168		(94	)		-		253
	Available-for-sale securities:
	Others		-		495		-			-		495
	Short-term investment		674		168		(94	)		-		748
		As of December 31, 2014
		Original		Gross		Gross			Provision		Fair
		cost		unrealized		unrealized			for		value
				gains		losses			decline
									in value
	Short-term investment:
	Trading securities		253		92		(172	)		-		173
	Available-for-sale securities:
	Listed equity securities		51,747		1,667		(9,856	)		—		43,558
	Bank financial products		14,505		—		—			—		14,505
	Others		500		—		—			—		500
	Short-term investment		67,005		1,759		(10,028	)		—		58,736
Long-term Investments, Available-for-sale Investments		As of December 31, 2014
		Original		Gross		Gross			Provision		Fair
		cost		unrealized		unrealized			for		value
				gains		losses			decline
									in value
	Long-term investment:
	Available-for-sale securities:
	Listed equity securities		57,335		9,988		(19,679	)		—		47,644

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Fair Value of Financial Assets and Liabilities Measured at Recurring Basis		As of December 31, 2013								As of December 31, 2014
		Fair Value Measurements at the Reporting Date Using								Fair Value Measurements at the Reporting Date Using
		Quoted prices in		Significant						Quoted prices in		Significant
		active markets		other		Significant				active markets		other		Significant
		for identical		observable		unobservable				for identical		observable		unobservable
		instruments		inputs		inputs		Total		instruments		inputs		inputs			Total
		(level 1)		(level 2)		(level 3)		balance		(level 1)		(level 2)		(level 3)			balance
	Cash equivalents-term deposits	$	683,994	$	-	$	-	$	683,994	$	1,129,833	$	-	$	-		$	1,129,833
	Short-term investments:
	Trading securities		253		-		-		253		173		-		-			173
	Available-for-sale investments
	Listed equity securities		-		-		-		-		43,558		-		-			43,558
	Bank financial products		-		-		-		-		-		14,505		-			14,505
	Others		-		495		-		495		-		500		-			500
	Long-term investments
	Listed equity securities		-		-		-		-		47,644		-		-			47,644
	Contingent consideration		-		-		-		-		-		-		(22,168	)		(22,168	)
	Total	$	684,247	$	495	$	-	$	684,742	$	1,221,208	$	15,005	$	(22,168	)	$	1,214,045
Reconciliation of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3)		Total
	Balance at December 31, 2013		-
	Addition in connection with business acquisition (Note 3(1)&(3))		20,951
	Increase in fair value		1,217
	Balance at December 31, 2014		22,168

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2014
Property and Equipment, Net [Abstract]
Schedule of Property and Equipment, Net		December 31,
		2013		2014
	Computer equipment and application software	$	149,877	$	276,078
	Building		46,471		88,036
	Office building related facility and machines		14,022		27,988
	Furniture and vehicles		4,672		8,656
	Leasehold improvements		1,354		6,092
	Construction in Progress		5,469		-
			221,865		406,850
	Less: Accumulated depreciation and amortization		58,001		134,824
	Property and equipment, net	$	163,864	$	272,026

Land_Use_Rights_Net_Tables

Land Use Rights, Net (Tables)	12 Months Ended
	Dec. 31, 2014
Land Use Rights, Net [Abstract]
Schedule of Land Use Rights, Net		December 31,
		2013		2014
	Land use rights	$	77,590	$	143,194
	Less: accumulated depreciation and amortization		1,892		4,087
	Land use rights, net	$	75,698	$	139,107

Goodwill_Tables

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill [Abstract]
Schedule of Goodwill		2013			2014
	Beginning balance	$	4,628		$	29,509
	Goodwill acquired in acquisitions of business		24,992			316,492
	Exchange rate differences		(111	)		(1,371	)
	Ending balance	$	29,509		$	344,630

Acquired_Intangible_Assets_Net1

Acquired Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2014
Acquired Intangible Assets, Net [Abstract]
Schedule of Definite-lived Intangible Assets		December 31,
		2013			2014
	Definite-lived
	Domain names	$	2,482		$	5,140
	Technology		12,013			28,043
	Non-compete agreement		3,985			13,026
	Customer relationship		2,973			5,110
	Distributor relationship		-			6,930
	Others		3,666			8,926
	Total acquired definite-lived intangible assets		25,119			67,175
	Less: Accumulated amortization
	Domain names		(859	)		(1,252	)
	Technology		(3,450	)		(7,627	)
	Non-compete agreement		(1,584	)		(4,426	)
	Customer relationship		(507	)		(1,552	)
	Distributor relationship		-			(347	)
	Others		(1,322	)		(3,225	)
	Less: Impairment loss
	Domain names		(424	)		(413	)
	Technology		(887	)		(859	)
	Others		(72	)		(70	)
	Acquired definite-lived intangible assets, net	$	16,014		$	47,404
Schedule of Indefinite-lived Intangible Assets		December 31,
		2013			2014
	Indefinite-lived
	Domain names	$	371		$	2,937
	Trademarks and others		2,200			2,253
	Total acquired indefinite-lived intangible assets		2,571			5,190
	Less: Accumulated impairment loss
	Domain names		(288	)		(282	)
	Trademarks and others		(1,049	)		(1,023	)
	Accumulated impairment loss		(1,337	)		(1,305	)
	Acquired indefinite-lived intangible assets, net	$	1,234		$	3,885

Accrued_Expenses_and_Other_Cur1

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities		December 31,
		2013		2014
	Payable related to investment and acquisition	$	365	$	64,545
	Payable for third-party service fee		30,017		56,772
	Accrued agent rebates		16,891		53,090
	Accrued payroll		19,217		37,540
	Other tax payable		12,094		21,097
	Deposits from advertising customers		10,060		19,747
	Payable for purchasing long-term assets		20,861		15,507
	Accrued interest expenses of convertible senior notes (see note 14)		4,808		10,062
	Other current liabilities		6,105		20,471
	Total	$	120,418	$	298,831

Deferred_Revenue_Tables

Deferred Revenue (Tables)	12 Months Ended
	Dec. 31, 2014
Deferred Revenue [Abstract]
Schedule of Deferred Revenue		December 31,
		2013		2014
	Deferred revenue - current
	Customers advance	$	33,979	$	52,548
	Deferred income		12,653		20,342
	Total deferred revenue - current	$	46,632	$	72,890
	Deferred revenue - noncurrent
	Customers advance	$	1,612	$	1,606
	Deferred income		1,932		675
	Total deferred revenue - noncurrent	$	3,544	$	2,281

Longterm_Debt_Tables

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Long-term Debt [Abstract]
Interest Expense of Long-term Debt		For the year ended
		31-Dec-14
	Interest expense at an annual rate of 2.50%	$	15,981
	Interest expense at an annual rate of 0.50%	$	1,042
	Interest expense at an annual rate of 1.75%	$	3,614
	Amortization of debt issuance costs	$	3,373
	Total interest expense	$	24,010
		31-Dec-13
	Interest expense at an annual rate of 2.50%	$	4,808
	Amortization of debt issuance costs	$	743
	Total interest expense	$	5,551

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Components of Income Tax Expense		For the year ended December 31,
		2012			2013			2014
	Current income tax expense	$	12,062		$	22,382		$	69,693
	Deferred income tax (benefit) expense		(683	)		1,041			(18,268	)
	Total income tax expense	$	11,379		$	23,423		$	51,425
Components of Deferred Tax Assets and Liabilities		December 31,
		2013			2014
	Current deferred tax assets
	Accrued payroll	$	2,889		$	5,141
	Provision of allowance for doubtful accounts		92			478
	Deferred revenue-current		306			660
	Less: Valuation allowance		(158	)		(1,435	)
	Current deferred tax assets, net		3,129			4,844
	Noncurrent deferred tax assets
	Deferred revenue-noncurrent		383			339
	Intangible assets		266			953
	Fixed assets		66			100
	Subsidy income		231			270
	Net operating loss carry forwards		4,592			9,193
	Promotion fee		-			13,894
	Unrealized loss on available-for-sale investments		-			2,462
	Less: Valuation allowance		(4,592	)		(10,846	)
	Noncurrent deferred tax assets, net		946			16,365
	Noncurrent deferred tax liabilities
	Acquired intangible assets		2,676			8,159
	Unrealized gain on available-for-sale investments		-			357
	Noncurrent deferred tax liabilities	$	2,676		$	8,516
Effective Income Tax Rate Reconciliation		For the year ended December 31,
		2012			2013			2014
	Income before income tax expense	$	62,695		$	124,019		$	286,494
	PRC statutory income tax rate		25	%		25	%		25	%
	Income tax expense at the statutory income tax rate		15,674			31,005			71,624
	Permanent differences		870			1,663			5,506
	Effect of different income tax calculation method required by tax bureau		67			48			(5	)
	Effect of tax exempt status in Cayman Islands and other jurisdictions		12,217			30,241			24,701
	Effect of different income tax rate in Hong Kong		(25	)		168			273
	Effect of income tax holiday and preferential tax rates		(17,844	)		(43,460	)		(58,529	)
	Changes in valuation allowance		420			3,758			7,855
	Income tax expense	$	11,379		$	23,423		$	51,425

Net_Income_Per_Share_Tables

Net Income Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Net Income Per Share [Abstract]
Computation of Basic and Diluted Net Income per Share			2012		2013		2014
	Net income attributable to Qihoo 360 Technology Co. Ltd			46,746		99,652		222,768
	Undistributed earnings allocated to participating unvested shares (i)			2,049		3,175		3,848
	Net income attributable to Class A and Class B ordinary shareholders for computing basic net income per ordinary share			44,697		96,477		218,920
	Net income attributable to nonvested shareholders for computing basic net income per participating unvested shares (i)			2,049		3,175		3,848
	Weighted average ordinary shares outstanding used in computing basic net income per Class A and Class B ordinary share			168,709,221		174,727,288		181,909,716
	Weighted average shares used in calculating net income per participating unvested share-basic			7,733,645		5,749,393		3,197,500
	Effect of dilutive securities:
	Plus incremental weighted average ordinary shares from assumed exercise of stock options and nonvested shares using the treasury stock method			7,180,369		12,560,169		12,384,156
	Weighted average ordinary shares outstanding used in computing diluted net income per Class A and Class B ordinary share (i)			183,623,235		193,036,850		197,491,372
	Net income per Class A and Class B ordinary share-basic			0.26		0.55		1.2
	Net income per participating unvested share-basic			0.26		0.55		1.2
	Net income per Class A and Class B ordinary share-diluted			0.25		0.52		1.13
		(i)	The net income attributable to Qihoo 360 Technology Co. Ltd. was allocated among Class A and Class B ordinary shares, and certain nonvested shares pro rata on the basis of their right to participate in dividends.

Sharebased_Compensation_Tables

Share-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Fair Value of Share Options, Valuation Assumptions		Year ended December 31,
		2012		2013	2014
	Risk-free interest rate	2.83% - 3.35%		3.40% - 4.02%	3.96%~4.61%
	Expected life (years)	6.35		6.35	5.85~6.35
	Volatility	46.98% - 74%		46.04% - 46.68%	44.28%~46.02%
	Dividend yield	-		-	-
Summary of Share Options Activities					Weighted average		Weighted average		Aggregate
					exercise price		remaining contractual		intrinsic value
		Number of options			per option		life (Years)		(in thousands)
	Outstanding at December 31, 2013		11,482,513		$	10.04		7.55		512,964
	Granted		258,500			45.35
	Exercised		(1,833,657	)		7.96
	Expired		(3,000	)		58.49
	Forfeited		(720,366	)		20.23
	Outstanding at December 31, 2014		9,183,990		$	10.57		6.61		257,557
	Vested and exercisable at December 31, 2014		4,913,833			7		6.09		153,647
	Vested and expect to vest at December 31, 2014		16,690,231			8.32		6.28		502,394
Summary of Nonvested Shares Activities					Weighted average
					fair value per
		Number of			nonvested share
		nonvested shares			at the grant date
	Outstanding at December 31, 2013		10,070,794		$	15.44
	Granted		2,734,139			56.27
	Vested		(3,086,753	)		12.79
	Forfeited		(1,174,065	)		33.32
	Outstanding at December 31, 2014		8,544,115		$	26.85
	Vested and to be transferred to grantees at December 31, 2014		21,503,321
	Vested and expect to vest at December 31, 2014		31,574,115

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
Future Minimum Lease Payments under Operating Agreements	2015	27,437
	2016	6,460
	2017	4,061
	2018	2,070
	2019 and after	4,641
		44,669
Future Minimum Lease Payments under Other Commitments	2015	26,644
	2016	26,644
	2017	26,644
	2018	22,269
	2019 and after	27,977
		130,178

Segments_and_Geographic_Inform1

Segments and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segments and Geographic Information [Abstract]
Components of Revenues		For the years ended December 31,
		2012			2013			2014
	Revenues:
	Internet services	$	328,882		$	671,088		$	1,370,695
	Others		150			-			19,965
			329,032			671,088			1,390,660
	Cost of revenues:
	Internet services		(32,762	)		(87,838	)		(297,645	)
	Others		(40	)		-			(7,817	)
			(32,802	)		(87,838	)		(305,462	)
	Gross profit:
	Internet services		296,120			583,250			1,073,050
	Others		110			-			12,148
			296,230			583,250			1,085,198
	Operating expenses:
	Product development		(156,269	)		(255,248	)		(406,250	)
	Selling and marketing		(58,178	)		(110,104	)		(333,701	)
	General and administrative		(35,643	)		(117,148	)		(94,260	)
	Total operating expenses		(250,090	)		(482,500	)		(834,211	)
	Subsidy income		2,570			2,349			8,506
	Income from operations	$	48,710		$	103,099		$	259,493

Additional_Information_Financi1

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Tables)	12 Months Ended
	Dec. 31, 2014
Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company [Abstract]
Condensed Financial Information of Parent Company Balance Sheets		December 31,
		2013			2014
	ASSETS
	Current assets:
	Cash and cash equivalents	$	695,515		$	1,242,129
	Restricted cash		300			-
	Short-term investments		253			6,839
	Prepaid expenses and other current assets		3,206			111,872
	Amounts due from subsidiaries and VIEs		167,395			459,303
	Deferred tax assets - current		306			412
	Total current assets		866,975			1,820,555
	Acquired intangible assets, net		2,449			1,205
	Investments in subsidiaries and VIEs		449,893			799,123
	Long-term investments		17,139			45,211
	Other noncurrent assets		11,707			26,964
	Deferred tax assets - noncurrent		383			103
	TOTAL ASSETS	$	1,348,546		$	2,693,161
	LIABILITIES
	Current liabilities:
	Accrued expenses and other current liabilities		6,760			12,455
	Deferred revenue-current		1,150			1,539
	Amounts due to subsidiaries and VIEs		2,306			15,184
	Total current liabilities		10,216			29,178
	Deferred revenue-noncurrent		1,437			385
	Long-term debt		600,000			1,635,000
	TOTAL LIABILITIES	$	611,653		$	1,664,563
	EQUITY
	Qihoo 360 Technology Co. Ltd. shareholders' equity
	Class A ordinary shares ($0.001 par value; 378,000,000 and 378,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 134,123,218 and 147,485,168 shares issued and outstanding as of December 31, 2013 and 2014, respectively)		134			147
	Class B ordinary shares ($0.001 par value; 122,000,000 and 122,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 54,767,703 and 45,931,163 shares issued and outstanding as of December 31, 2013 and 2014, respectively)		55			46
	Treasury stock		(139	)		(139	)
	Additional paid-in capital		568,675			669,760
	Accumulated other comprehensive income (loss)		20,380			(11,772	)
	Retained earnings		147,788			370,556
	Total shareholders' equity		736,893			1,028,598
	TOTAL EQUITY		736,893			1,028,598
	TOTAL LIABILITIES AND EQUITY	$	1,348,546		$	2,693,161
Condensed Financial Information of Parent Company Statements of Operations		For the years ended December 31,
		2012			2013			2014
	Cost of revenues		4			-			-
	Operating expenses:
	Selling and marketing		21,289			15,519			15,666
	General and administrative		10,815			73,372			19,305
	Product development		21,782			38,211			59,375
	Total operating expenses		53,886			127,102			94,346
	Loss from operations		(53,890	)		(127,102	)		(94,346	)
	Interest income		4,702			6,341			20,264
	Interest expense		-			(5,551	)		(24,010	)
	Other income		1,277			1,197			1,447
	Exchange gain (loss)		412			5,100			(11,520	)
	(Loss) gain in connection with short-term investments		(52	)		327			10,230
	Gain in connection with long-term investments		-			413			-
	Loss before income tax expense and earnings from subsidiary and VIEs		(47,551	)		(119,275	)		(97,935	)
	Income in earnings of subsidiaries and VIEs		94,639			219,247			321,088
	Income before income tax expense		47,088			99,972			223,153
	Income tax expense		(342	)		(320	)		(385	)
	Net income attributable to Qihoo 360 Technology Co. Ltd.	$	46,746		$	99,652		$	222,768
Condensed Financial Information of Parent Company Statements of Comprehensive Income		For the years ended December 31,
		2012			2013			2014
	Net income	$	46,746		$	99,652		$	222,768
	Other comprehensive income (loss), net of tax:
	Foreign currency translation adjustments		2,851			11,266			(42,342	)
	Unrealized loss on available-for-sale investments		-			-			10,190
	Other comprehensive income (loss)		2,851			11,266			(32,152	)
	Comprehensive income		49,597			110,918			190,616
	Add: Comprehensive loss attributable to noncontrolling interest		-			-			-
	Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.	$	49,597		$	110,918		$	190,616
Condensed Financial Information of Parent Company Statements of Changes in Equity																			Total
																			Qihoo 360
														Accumulated			(Accumulated		Technology
											Additional			other			deficit)		Co. Ltd.
		Ordinary shares									paid-in			comprehensive			retained		shareholders'
		Shares			Amount			Treasury Stock			capital			income (loss)			earnings		equity
	Balance as of January 1, 2012		179,029,251		$	179		$	-		$	363,021		$	6,263		$	1,390	$	370,853
	Issuance of ordinary shares in connection with share-based compensation arrangements		3,512,394			3			-			-			-			-		3
	Share-based compensation		-			-			-			50,605			-			-		50,605
	Issuance of ordinary shares in connection with exercise of options		1,615,452			2			-			6,963			-			-		6,965
	Disposal of noncontrolling interest in subsidiaries		-			-			-			73			-			-		73
	Net income		-			-			-			-			-			46,746		46,746
	Other comprehensive income		-			-			-			-			2,851			-		2,851
	Balance as of December 31, 2012		184,157,097			184			-			420,662			9,114			48,136		478,096
	Issuance of ordinary shares in connection with share-based compensation arrangements		561,517			1			-			-			-			-		1
	Share repurchase		(14,544	)		-			(139	)		-			-			-		(139	)
	Share-based compensation		-			-			-			121,087			-			-		121,087
	Issuance of ordinary shares in connection with business acquisition		204,466			-			-			7,864			-			-		7,864
	Issuance of ordinary shares in connection with exercise of options		3,982,385			4			-			19,067			-			-		19,071
	Disposal of noncontrolling interest in subsidiaries		-			-			-			(5	)		-			-		(5	)
	Net income		-			-			-			-			-			99,652		99,652
	Other comprehensive income		-			-			-			-			11,266			-		11,266
	Balance as of December 31, 2013		188,890,921			189			(139	)		568,675			20,380			147,788		736,893
	Issuance of ordinary shares in connection with share-based compensation arrangements		2,691,753			2			-			-			-			-		2
	Share-based compensation		-			-			-			90,392			-			-		90,392
	Issuance of ordinary shares in connection with exercise of options		1,833,657			2			-			15,064			-			-		15,066
	Acquisition of additional equity interests in subsidiaries		-			-			-			(4,371	)		-			-		(4,371	)
	Net income		-			-			-			-			-			222,768		222,768
	Other comprehensive loss		-			-			-			-			(32,152	)		-		(32,152	)
	Balance as of December 31, 2014		193,416,331		$	193		$	(139	)	$	669,760		$	(11,772	)	$	370,556	$	1,028,598
Condensed Financial Information of Parent Company Statements of Cash Flow		For the years ended December 31,
		2012			2013			2014
	Cash flows from operating activities
	Net income		46,746			99,652			222,768
	Adjustments to reconcile net income to net cash provided by operating activities
	Share-based compensation		50,605			121,087			89,686
	Gain from investments in subsidiaries and VIEs		(94,639	)		(219,247	)		(321,089	)
	Depreciation and amortization		582			1,476			1,243
	Loss (gain) in connection with short-term investments		52			(327	)		(10,230	)
	Gain in connection with long-term investments		-			(413	)		-
	Prepaid expenses and other current assets		(2,307	)		463			(3,788	)
	Deferred taxes		(178	)		(53	)		174
	Other noncurrent assets		-			743			3,373
	Accrued expenses and other current liabilities		149			5,488			5,694
	Deferred revenue		700			215			(662	)
	Amount due from/to subsidiaries and VIEs		(21,816	)		(128,738	)		(280,582	)
	Net cash used in operating activities		(20,106	)		(119,654	)		(293,413	)
	Cash flows from investing activities
	(Increase) decrease in restricted cash		(300	)		-			300
	Purchase of intangible assets		(1,500	)		(1,500	)		-
	Purchase of short-term investments		-			(510	)		(30,025	)
	Proceeds from sale of short-term investments		-			762			35,335
	Capital contribution for long-term investments		(450	)		(15,760	)		(39,928	)
	Dividends received from a cost method investee		-			413			-
	Investment in subsidiaries		(1,200	)		-			(53,771	)
	Net cash used in investing activities		(3,450	)		(16,595	)		(88,089	)
	Cash flows from financing activities
	Proceeds from issuance of Convertible Senior Notes (net of issuance costs of $12,150 and $18,630 in 2013 and 2014, respectively)		-			587,850			1,016,370
	Proceeds from exercise of share options		2,089			23,678			15,947
	Payment for share repurchase		(139	)		-			(104,201	)
	Net cash provided by financing activities		1,950			611,528			928,116
	Net (decrease) increase in cash and cash equivalents		(21,606	)		475,279			546,614
	Cash and cash equivalents at beginning of year		241,842			220,236			695,515
	Cash and cash equivalents at end of year		220,236			695,515			1,242,129

Organization_and_Principal_Act2

Organization and Principal Activities (The VIE Arrangements) (Details)	12 Months Ended
	Dec. 31, 2014
Business operation agreements [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years
Technology consulting and services agreements [Member] | Minimum [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	3 years
Technology consulting and services agreements [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years
Equity disposition agreements [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years
Loan agreements [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years
Equity interest in VIEs	100.00%
Equity pledge agreements [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years
Power of attorney [Member]
Variable Interest Entity [Line Items]
Term of contractual arrangements	10 years

Organization_and_Principal_Act3

Organization and Principal Activities (Schedule of Variable Interest Entities) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Cash and cash equivalents	$1,645,234	$1,013,465	$380,664	$343,731
Restricted cash	2,053	2,368
Total current assets	2,096,149	1,157,717
Property and equipment, net	272,026	163,864
Acquired intangible assets, net	51,289	17,248
Other noncurrent assets	97,025	39,621
Total assets	3,331,570	1,568,896
Deferred revenue-current	72,890	46,632
Total current liabilities	540,229	208,598
Total liabilities	2,189,302	814,818
Revenues	1,390,660	671,088	329,032
Net income	216,163	97,849	46,471
Net cash provided by operating activities	380,299	210,226	117,788
Net cash used in investing activities	-661,494	-196,874	-83,927
Net cash provided by (used in) financing activities	919,714	613,498	1,986
Net increase in cash and cash equivalents	631,769	632,801	36,933
VIEs and VIEs' Subsidiaries [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	239,903	116,575
Restricted cash	2,053	2,068
Accounts receivable and other current assets	242,388	61,177
Total current assets	484,344	179,820
Property and equipment, net	138,345	91,861
Acquired intangible assets, net	32,292	9,681
Other noncurrent assets	301,070	37,778
Total noncurrent assets	471,707	139,320
Total assets	956,051	319,140
Deferred revenue-current	44,869	30,717
Accounts payable and other current liabilities	322,968	106,894
Total current liabilities	367,837	137,611
Total noncurrent liabilities	9,611	2,235
Total liabilities	377,448	139,846
Revenues	1,069,308	527,646	303,200
Net income	451,191	263,514	150,408
Net cash provided by operating activities	439,351	129,175	75,983
Net cash used in investing activities	-305,996	-72,678	-50,951
Net cash provided by (used in) financing activities	-10,028	1,970	36
Net increase in cash and cash equivalents	$123,327	$58,467	$25,068

Organization_and_Principal_Act4

Organization and Principal Activities (Narrative) (Details) (VIEs and VIEs' Subsidiaries [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
VIEs and VIEs' Subsidiaries [Member]
Variable Interest Entity [Line Items]
Amount payable by the VIEs and their subsidiaries to WOFEs related to the service fees	$3.30	$0.10	$2.30
Percentage of consolidated revenues VIEs contribute	76.90%	78.60%	92.10%
Percentage of consolidated total assets VIEs accounted for	28.70%	20.30%
Percentage of consolidated total liabilities VIEs accounted for	17.20%	17.20%
Percentage of Group's employees hired by VIEs and their subsidiaries	51.20%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Property and Equipment, Estimated Useful Lives) (Details)	12 Months Ended
	Dec. 31, 2014
Computer equipment and application software [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	3-6 years
Building [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	44-60 years
Office building related facility and machines [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10-15 years
Furniture and vehicles [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	3-10 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	lesser of the lease term or the estimated useful life of the assets

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Acquired Intangible Assets, Estimated Useful Lives) (Details)	12 Months Ended
	Dec. 31, 2014
Domain names [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	3 years
Domain names [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	10 years
Source code [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	5 years
Source code [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	8 years
Technology [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	2 years
Technology [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	10 years
Non-compete agreement [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	1 year
Non-compete agreement [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	6 years
Operating license [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	5 years
Operating license [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	30 years
Trademarks [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	3 years
Trademarks [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	10 years
User base [Member] | Minimum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	6 months
User base [Member] | Maximum [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	1 year
Customer relationship [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	3 years
Distributor relationship [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	5 years
Backlog [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Estimated useful lives	3 years

Summary_of_Significant_Account5

Summary of Significant Accounting Policies (Concentration of Credit Risk) (Details) (Credit Concentration Risk [Member])	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
A [Member] | Total revenue [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	0.00%	[1]	0.00%	[1]	5.00%
B [Member] | Total revenue [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	0.00%	[1]	0.00%	[1]	10.00%
B [Member] | Accounts receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	0.00%	[1]	32.00%
C [Member] | Accounts receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%		0.00%	[1]
[1]	means less than 10%

Summary_of_Significant_Account6

Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Significant Accounting Policies [Abstract]
Construction-in-progress	$0
Impairment loss on goodwill	0	107,000	1,151,000
Maximum ownership percentage of limited partnerships accounted for using cost method	5.00%
Significant influence existence criteria, minimum ownership interest	20.00%
Significant influence existence criteria, maximum ownership interest	50.00%
VAT and related surcharges rate, minimum	3.21%
VAT and related surcharges rate, maximum	19.04%
Business tax and VAT included in revenues and cost of revenues	80,514,000	39,909,000	18,434,000
Advertising costs	231,198,000	62,301,000	21,082,000
Subsidy income	$8,506,000	$2,349,000	$2,570,000
Minimum likelihood of uncertain being sustained for uncertain income tax position being recognized	50.00%

Acquisitions_Narrative_of_Inte

Acquisitions (Narrative of Internet Service Business Acquired in January 2014) (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2014	Jan. 31, 2014
Business Acquisition [Line Items]
Consolidated net revenue contributed by investee	$1,085,198,000	$583,250,000	$296,230,000
Consolidated net loss contributed by investee	-216,163,000	-97,849,000	-46,471,000
Game platform business [Member]
Business Acquisition [Line Items]
Consideration of selling portion of acquired business				12,000,000
Net carrying value of disposed business				12,000,000
Goodwill allocated to the disposed business				9,951,000
Recognized gain or loss for disposal				0
Internet service company acquired in January 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired					100.00%
Purchase consideration					66,146,000
Initial consideration, cash					47,363,000
Contingent consideration, cash					20,000,000
Fair value of contingent consideration					18,783,000
Fair value change in contingent consideration	1,217,000
Consolidated net revenue contributed by investee	138,919,000
Consolidated net loss contributed by investee	$7,504,000

Acquisitions_Allocation_of_Pur

Acquisitions (Allocation of Purchase Price, Internet Service Business Acquired in January 2014) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$344,630	$29,509	$4,628
Internet service company acquired in January 2014 [Member]
Business Acquisition [Line Items]
Cash				14,730
Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities				-18,238
Goodwill				60,612
Deferred tax liability				-3,014
Total				66,146
Internet service company acquired in January 2014 [Member] | Non-compete agreement [Member]
Business Acquisition [Line Items]
Intangible assets				5,438
Internet service company acquired in January 2014 [Member] | Domain name [Member]
Business Acquisition [Line Items]
Intangible assets				3,008
Internet service company acquired in January 2014 [Member] | Technology [Member]
Business Acquisition [Line Items]
Intangible assets				2,314
Internet service company acquired in January 2014 [Member] | User base [Member]
Business Acquisition [Line Items]
Intangible assets				$1,296

Acquisitions_Narrative_of_Inte1

Acquisitions (Narrative of Internet Service Business Acquired in May 2014) (Details) (USD $)	12 Months Ended			1 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-14
Business Acquisition [Line Items]
Consolidated net revenue contributed by investee	$1,085,198	$583,250	$296,230
Consolidated net loss contributed by investee	-216,163	-97,849	-46,471
Internet service company acquired in May 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired				60.00%
Purchase consideration				134,332
Cash consideration, paid				124,332
Cash consideration, held back				10,000
Consolidated net revenue contributed by investee	25,946
Consolidated net loss contributed by investee	$5,829

Acquisitions_Allocation_of_Pur1

Acquisitions (Allocation of Purchase Price, Internet Service Business Acquired in May 2014) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-14
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$344,630	$29,509	$4,628
Internet service company acquired in May 2014 [Member]
Business Acquisition [Line Items]
Cash				49,564
Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities				-10,372
Goodwill				148,751
Deferred tax liability				-2,076
Non-controlling interest				-65,375
Total				134,332
Internet service company acquired in May 2014 [Member] | Technology [Member]
Business Acquisition [Line Items]
Intangible assets				9,377
Internet service company acquired in May 2014 [Member] | Non-compete agreement [Member]
Business Acquisition [Line Items]
Intangible assets				3,259
Internet service company acquired in May 2014 [Member] | Customer relationship [Member]
Business Acquisition [Line Items]
Intangible assets				$1,204

Acquisitions_Narrative_of_Ente

Acquisitions (Narrative of Enterprise Information Security Business) (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2014
Business Acquisition [Line Items]
Consolidated net revenue contributed by investee	$1,085,198,000	$583,250,000	$296,230,000
Consolidated net gain contributed by investee	216,163,000	97,849,000	46,471,000
Enterprise information security business acquired in October 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired				75.10%
Purchase consideration				126,065,000
Initial consideration, cash				123,897,000
Cash consideration, paid				89,938,000
Contingent consideration, cash				2,168,000
Fair value change in contingent consideration	0
Consolidated net revenue contributed by investee	18,934,000
Consolidated net gain contributed by investee	$5,426,000

Acquisitions_Allocation_of_Pur2

Acquisitions (Allocation of Purchase Price, Enterprise Information Security Business) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2014
In Thousands, unless otherwise specified
Business Acquisition [Line Items]
Goodwill	$344,630	$29,509	$4,628
Enterprise information security business acquired in October 2014 [Member]
Business Acquisition [Line Items]
Cash				50,292
Other net liabilities acquired, excluding intangible assets and related deferred tax liabilities				-22,324
Goodwill				115,757
Deferred tax liability				-2,353
Non-controlling interest				-30,994
Total				126,065
Enterprise information security business acquired in October 2014 [Member] | Distributor relationship [Member]
Business Acquisition [Line Items]
Intangible assets				7,006
Enterprise information security business acquired in October 2014 [Member] | Technology [Member]
Business Acquisition [Line Items]
Intangible assets				3,436
Enterprise information security business acquired in October 2014 [Member] | Operating license [Member]
Business Acquisition [Line Items]
Intangible assets				1,808
Enterprise information security business acquired in October 2014 [Member] | Customer relationships [Member]
Business Acquisition [Line Items]
Intangible assets				1,303
Enterprise information security business acquired in October 2014 [Member] | Backlog [Member]
Business Acquisition [Line Items]
Intangible assets				1,254
Enterprise information security business acquired in October 2014 [Member] | Trademarks [Member]
Business Acquisition [Line Items]
Intangible assets				$880

Acquisitions_Pro_Forma_Informa

Acquisitions (Pro Forma Information Of Aggregated Individually Material Acquirees Acquired in 2014) (Details) (Aggregated individually material acquirees acquired in 2014 [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Aggregated individually material acquirees acquired in 2014 [Member]
Business Acquisition [Line Items]
Pro forma revenue	$1,415,532	$841,573
Pro forma net income (loss)	$212,558	$106,846
Pro forma earnings (loss) per ordinary share-basic	$1.15	$0.59
Pro forma earnings (loss) per ordinary share-diluted	$1.08	$0.55

Acquisitions_Other_Acquisition

Acquisitions (Other Acquisitions) (Details) (USD $)	1 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	31-May-14	Oct. 31, 2014	Nov. 30, 2014	31-May-13	Jul. 31, 2013	Sep. 30, 2013	Nov. 30, 2013	Sep. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill									$29,509	$4,628	$344,630
Internet security business acquired in May 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired	60.00%
Cash consideration	1,092
Goodwill	122
Internet security business acquired in October 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired		100.00%
Cash consideration		684
Goodwill		289
Internet service business acquired in November 2014 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired			100.00%
Cash consideration			1,302
Goodwill			912
Internet service business acquired in May 2013 [Member]
Business Acquisition [Line Items]
Cash consideration				1,790
Goodwill				1,248
Internet data center business ("Entity P") acquired in May 2013 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired				51.00%
Cash consideration				3,257
Goodwill				317
Overseas internet service company acquired in July 2013 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired					51.00%
Goodwill					8,319
Overseas internet service company acquired in July 2013 [Member] | Chairman and Chief Executive Officer of the Company [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired					28.53%
Overseas internet service company acquired in July 2013 [Member] | Ordinary shares [Member]
Business Acquisition [Line Items]
Business acquisition, value of shares issuable					7,864
Business acquisition, number of shares issuable					204,466
Overseas internet service company acquired in July 2013 [Member] | Ordinary shares [Member] | Chairman and Chief Executive Officer of the Company [Member]
Business Acquisition [Line Items]
Business acquisition, value of shares issuable					1,989
Business acquisition, number of shares issuable					51,722
Overseas internet service company acquired in July 2013 [Member] | ADS [Member] | Chairman and Chief Executive Officer of the Company [Member]
Business Acquisition [Line Items]
Business acquisition, number of shares issuable					34,481
Internet service company with 80% equity interest owned by Group [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired						60.00%
Cash consideration						7,966
Goodwill						8,762
Internet service company with 51% equity interest owned by Group [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired							51.00%
Cash consideration							10,000
Goodwill							6,346
Software development business acquired in September 2012 [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired								65.00%
Cash consideration								312
Cash consideration, paid									$127	$185

Acquisitions_Pro_Forma_Informa1

Acquisitions (Pro Forma Information Of Aggregated Individually Material Acquirees Acquired in 2013) (Details) (Aggregated individually material acquirees acquired in 2013 [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Aggregated individually material acquirees acquired in 2013 [Member]
Business Acquisition [Line Items]
Pro forma revenue	$676,414	$336,774
Pro forma net income	$95,937	$43,857
Pro forma earnings (loss) per ordinary share-basic	$0.53	$0.25
Pro forma earnings (loss) per ordinary share-diluted	$0.50	$0.24

Accounts_Receivable_Schedule_o

Accounts Receivable (Schedule of Accounts Receivable) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Accounts receivable consists of:
Accounts receivable	$156,697	$54,743
Allowance for doubtful accounts	-2,410	-145	-213	-68
Accounts receivable, net	$154,287	$54,598

Accounts_Receivable_Movement_o

Accounts Receivable (Movement of Allowance for Doubtful Accounts) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Movement of allowance for doubtful accounts
Balance at beginning of year	$145	$213	$68
Addition in connection with business acquisition	2,020	0	0
Charge to expense	349	157	154
Write offs during the year	-74	-229	-10
Exchange rate differences	-30	4	1
Balance at end of year	$2,410	$145	$213

Prepaid_Expenses_and_Other_Cur2

Prepaid Expenses and Other Current Assets (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Prepaid Expenses and Other Current Assets [Abstract]
Prepayment for share repurchase (i)	$104,201	[1]	$0
Prepaid expenses and other receivables	46,266		19,921
Advance to suppliers	34,238		15,577
Prepayment related to investments (ii)	29,704	[2]	12,325	[2]
Interest receivable	5,314		3,219
Receivables related to share options (iii)	1,473	[3]	29,496	[3]
Prepaid expenses and other current assets	$221,196		$80,538
[1]	The board of directors of the Group approved a $200 million share repurchase program in October 2014. As of December 31, 2014, the Company prepaid $104 million for the repurchase of shares. The Company completed the share repurchase program in February 2015.
[2]	The Group made several payments to establish new companies with other independent third parties. The prepayments will be recorded as long-term investments when the investees are legally established.
[3]	Amount represents the exercise cost to be received by the Group from a trading institution after the Group's employees exercised their stock options through such institution.

Prepaid_Expenses_and_Other_Cur3

Prepaid Expenses and Other Current Assets (Narrative) (Details) (ADS [Member], USD $)	Oct. 31, 2014	Jan. 31, 2012
In Millions, unless otherwise specified
ADS [Member]
Schedule of Prepaid Expenses and Other Current Assets [Line Items]
Stock repurchase program, authorized amount	$200	$50

Investments_Shortterm_Investme

Investments (Short-term Investments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Short-term Investments [Line Items]
Original cost	$67,005,000	$674,000
Gross unrealized gains	1,759,000	168,000
Gross unrealized losses	-10,028,000	-94,000
Provision for decline in value	0	0
Fair value	58,736,000	748,000
Impairment loss on short-term investments	0	0	0
Trading securities [Member]
Schedule of Short-term Investments [Line Items]
Original cost	253,000	179,000
Gross unrealized gains	92,000	168,000
Gross unrealized losses	-172,000	-94,000
Provision for decline in value	0	0
Fair value	173,000	253,000
Listed equity securities [Member]
Schedule of Short-term Investments [Line Items]
Original cost	51,747,000
Gross unrealized gains	1,667,000
Gross unrealized losses	-9,856,000
Provision for decline in value	0
Fair value	43,558,000
Bank financial products [Member]
Schedule of Short-term Investments [Line Items]
Original cost	14,505,000
Gross unrealized gains	0
Gross unrealized losses	0
Provision for decline in value	0
Fair value	14,505,000
Others [Member]
Schedule of Short-term Investments [Line Items]
Original cost	500,000	495,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Provision for decline in value	0	0
Fair value	$500,000	$495,000

Investments_Longterm_Investmen

Investments (Long-term Investments, Cost-method Investments) (Details) (USD $)	12 Months Ended			1 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014	Jul. 31, 2012
Schedule of Cost-method Investments [Line Items]
Carrying amount of cost method investments	$137,134	$46,012
Maximum ownership percentage in cost method investments	20.00%
Impairment loss on cost method investments	578	867	761
Internet service company [Member]
Schedule of Cost-method Investments [Line Items]
Cost method investments, consideration				$17,445	$482
Equity interest purchased in cost-method investments					26.51%
Equity interest in cost-method investments	38.11%

Investments_Longterm_Investmen1

Investments (Long-term Investments, Equity-method Investments) (Details) (USD $)	12 Months Ended			1 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2012	Nov. 30, 2011
Schedule of Equity Method Investments [Line Items]
Carrying amount of equity method investments	$130,201	$38,281		$130,201	$38,281
Minimum voting interests of equity method investments, percentage	10.00%
Maximum voting interests of equity method investments, percentage	65.00%
Loss from equity method investments	18,906	2,747	4,845
Impairment losses on equity method investments	1,943	4,137	1,541
Internet security company [Member]
Schedule of Equity Method Investments [Line Items]
Carrying amount of equity method investments	22,276			22,276
Equity interest purchased in equity-method investments							30.00%
Aggregate purchase price of equity-method investment				9,360	25,000	2,140
Equity interest in equity-method investment	40.80%			40.80%
Hardware develop company [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest purchased in equity-method investments				40.00%
Aggregate purchase price of equity-method investment				$17,568

Investments_Longterm_Investmen2

Investments (Long-term Investments, Available-for-sale Investments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Long-term Investments [Line Items]
Impairment loss on available-for-sale investments	$0	$0	$0
Available-for-sale securities [Member]
Schedule of Long-term Investments [Line Items]
Fair value	47,644,000	0
Listed equity securities [Member]
Schedule of Long-term Investments [Line Items]
Original cost	57,335,000
Gross unrealized gains	9,988,000
Gross unrealized losses	-19,679,000
Provision for decline in value	0
Fair value	$47,644,000

Fair_Value_Measurements_Fair_V

Fair Value Measurements (Fair Value of Financial Assets and Liabilities Measured at Recurring Basis) (Details) (Fair Value, Measurements, Recurring [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents-term deposits	$1,129,833	$683,994
Short-term investments:
Trading securities	173	253
Available-for-sale investments
Listed equity securities	43,558	0
Bank financial products	14,505	0
Others	500	495
Long-term investments
Listed equity securities	47,644	0
Contingent consideration	-22,168	0
Total	1,214,045	684,742
Quoted prices in active markets for identical instruments (level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents-term deposits	1,129,833	683,994
Short-term investments:
Trading securities	173	253
Available-for-sale investments
Listed equity securities	43,558	0
Bank financial products	0	0
Others	0	0
Long-term investments
Listed equity securities	47,644	0
Contingent consideration	0	0
Total	1,221,208	684,247
Significant other observable inputs (level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents-term deposits	0	0
Short-term investments:
Trading securities	0	0
Available-for-sale investments
Listed equity securities	0	0
Bank financial products	14,505	0
Others	500	495
Long-term investments
Listed equity securities	0	0
Contingent consideration	0	0
Total	15,005	495
Significant unobservable inputs (level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents-term deposits	0	0
Short-term investments:
Trading securities	0	0
Available-for-sale investments
Listed equity securities	0	0
Bank financial products	0	0
Others	0	0
Long-term investments
Listed equity securities	0	0
Contingent consideration	-22,168	0
Total	($22,168)	$0

Fair_Value_Measurements_Reconc

Fair Value Measurements (Reconciliation of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) (Fair Value, Measurements, Recurring [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Contingent consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2013	$0
Addition in connection with business acquisition (Note 3(1)&(3))	20,951,000
Increase in fair value	1,217,000
Balance at December 31, 2014	22,168,000
Assets measured at fair value on a recurring basis using significant unobservable inputs (level 3)	$0
Contingent consideration, part one [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount rate	13.00%
Contingent consideration, part two [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount rate	14.00%

Property_and_Equipment_Net_Det

Property and Equipment, Net (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$406,850	$221,865
Less: Accumulated depreciation and amortization	134,824	58,001
Property and equipment, net	272,026	163,864
Depreciation and amortization expenses	71,906	38,453	14,768
Computer equipment and application software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	276,078	149,877
Building [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	88,036	46,471
Office building related facility and machines [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,988	14,022
Furniture and vehicles [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,656	4,672
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,092	1,354
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$0	$5,469

Land_Use_Rights_Net_Details

Land Use Rights, Net (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Land Use Rights, Net [Abstract]
Land use rights	$143,194	$77,590
Less: accumulated depreciation and amortization	4,087	1,892
Land use rights, net	139,107	75,698
Land use rights, amortization expenses	2,256	1,714	140
Land use rights, future amortization expense per year in next five years	$3,278

Goodwill_Details

Goodwill (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Abstract]
Beginning balance	$29,509,000	$4,628,000
Goodwill acquired in acquisitions of business	316,492,000	24,992,000
Exchange rate differences	-1,371,000	-111,000
Ending balance	344,630,000	29,509,000	4,628,000
Impairment of goodwill	$0	$0	$0

Acquired_Intangible_Assets_Net2

Acquired Intangible Assets, Net (Definite-lived intangible assets) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	$67,175	$25,119
Acquired definite-lived intangible assets, net	47,404	16,014
Domain names [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	5,140	2,482
Less: Accumulated amortization	-1,252	-859
Less: Impairment loss	-413	-424
Technology [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	28,043	12,013
Less: Accumulated amortization	-7,627	-3,450
Less: Impairment loss	-859	-887
Non-compete agreement [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	13,026	3,985
Less: Accumulated amortization	-4,426	-1,584
Customer relationship [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	5,110	2,973
Less: Accumulated amortization	-1,552	-507
Distributor relationship [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	6,930	0
Less: Accumulated amortization	-347	0
Others [Member]
Acquired Definite-Lived Intangible Assets [Line Items]
Acquired definite-lived intangible assets, gross	8,926	3,666
Less: Accumulated amortization	-3,225	-1,322
Less: Impairment loss	($70)	($72)

Acquired_Intangible_Assets_Net3

Acquired Intangible Assets, Net (Narrative of Definite-lived intangible assets) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Intangible Assets, Net [Abstract]
Amortization expenses for intangible assets	$10,625,000	$4,176,000	$1,689,000
Expected Amortization Expense for Intangible Assets:
2015	12,571,000
2016	8,692,000
2017	7,688,000
2018	6,680,000
2019 and after	11,613,000
Impairment loss on definite-lived intangible assets	$0	$107,000	$1,151,000

Acquired_Intangible_Assets_Net4

Acquired Intangible Assets, Net (Indefinite-lived intangible assets) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Indefinite-lived Intangible Assets [Line Items]
Acquired indefinite-lived intangible assets, gross	$5,190,000	$2,571,000
Less: Accumulated impairment loss	-1,305,000	-1,337,000
Acquired indefinite-lived intangible assets, net	3,885,000	1,234,000
Impairment loss on indefinite-lived intangible assets	0	841,000	197,000
Domain names [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Acquired indefinite-lived intangible assets, gross	2,937,000	371,000
Less: Accumulated impairment loss	-282,000	-288,000
Trademarks and others [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Acquired indefinite-lived intangible assets, gross	2,253,000	2,200,000
Less: Accumulated impairment loss	($1,023,000)	($1,049,000)

Accrued_Expenses_and_Other_Cur2

Accrued Expenses and Other Current Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accrued Expenses and Other Current Liabilities [Abstract]
Payable related to investment and acquisition	$64,545	$365
Payable for third-party service fee	56,772	30,017
Accrued agent rebates	53,090	16,891
Accrued payroll	37,540	19,217
Other tax payable	21,097	12,094
Deposits from advertising customers	19,747	10,060
Payable for purchasing long-term assets	15,507	20,861
Accrued interest expenses of convertible senior notes (see note 14)	10,062	4,808
Other current liabilities	20,471	6,105
Total	$298,831	$120,418

Deferred_Revenue_Details

Deferred Revenue (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Revenue Arrangement [Line Items]
Deferred revenue - current	$72,890	$46,632
Deferred revenue - noncurrent	2,281	3,544
Customer advance [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue - current	52,548	33,979
Deferred revenue - noncurrent	1,606	1,612
Deferred income [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue - current	20,342	12,653
Deferred revenue - noncurrent	$675	$1,932

Longterm_Debt_Narrative_Detail

Long-term Debt (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 05, 2013	Aug. 06, 2014
Long-term debt [Line Items]
Value of Notes in long-term debt	$1,635,000,000	$600,000,000
Net proceeds received from issuance of the Notes	1,016,370,000	587,850,000	0
Unsecured Senior Notes [Member]
Long-term debt [Line Items]
Value of Notes in long-term debt	1,635,000,000
Accumulated debt issuance costs	30,780,000
Net proceeds received from issuance of the Notes	1,016,370,000	587,850,000
Unsecured Senior Notes [Member] | Non-contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption price, percentage of principal amount redeemed	100.00%
Unsecured Senior Notes [Member] | Contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption price, percentage of principal amount redeemed	100.00%
Unsecured Senior Notes [Member] | Redemption option at the option of the Company [Member]
Long-term debt [Line Items]
Redemption price, percentage of principal amount redeemed	100.00%
Redemption, description	On or after September 15, 2016, August 15, 2017 and August 15, 2019, the Company may redeem any or all of the 2018 Notes, 2020 Notes, and 2021 Notes, respectively, in cash at the redemption price, provided that the last reported sale price of the Company's ADSs for 20 or more trading days in a period of 30 consecutive trading days ending within 10 trading days immediately prior to the date of the redemption notice exceeds 130% of the applicable conversion price in effect on each such trading day.
Unsecured Senior Notes [Member] | 2018 Notes [Member]
Long-term debt [Line Items]
Unsecured Senior Notes, principal amount				600,000,000
Interest rate	2.50%
Unsecured Senior Notes [Member] | 2018 Notes [Member] | ADS [Member]
Long-term debt [Line Items]
Initial conversion price	$110.96
Unsecured Senior Notes [Member] | 2018 Notes [Member] | Non-contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Sep-16
Unsecured Senior Notes [Member] | 2018 Notes [Member] | Contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	5-Sep-13
Unsecured Senior Notes [Member] | 2018 Notes [Member] | Redemption option at the option of the Company [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Sep-16
Unsecured Senior Notes [Member] | 2020 Notes [Member]
Long-term debt [Line Items]
Unsecured Senior Notes, principal amount					517,500,000
Interest rate	0.50%
Unsecured Senior Notes [Member] | 2020 Notes [Member] | ADS [Member]
Long-term debt [Line Items]
Initial conversion price	$125.33
Unsecured Senior Notes [Member] | 2020 Notes [Member] | Non-contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Aug-17
Unsecured Senior Notes [Member] | 2020 Notes [Member] | Contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	6-Aug-14
Unsecured Senior Notes [Member] | 2020 Notes [Member] | Redemption option at the option of the Company [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Aug-17
Unsecured Senior Notes [Member] | 2021 Notes [Member]
Long-term debt [Line Items]
Unsecured Senior Notes, principal amount					$517,500,000
Interest rate	1.75%
Unsecured Senior Notes [Member] | 2021 Notes [Member] | ADS [Member]
Long-term debt [Line Items]
Initial conversion price	$120.77
Unsecured Senior Notes [Member] | 2021 Notes [Member] | Non-contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Aug-19
Unsecured Senior Notes [Member] | 2021 Notes [Member] | Contingent redemption option at the option of the holder [Member]
Long-term debt [Line Items]
Redemption period, start date	6-Aug-14
Unsecured Senior Notes [Member] | 2021 Notes [Member] | Redemption option at the option of the Company [Member]
Long-term debt [Line Items]
Redemption period, start date	15-Aug-19

Longterm_Debt_Interest_Expense

Long-term Debt (Interest Expense of Long-term Debt) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total interest expense	$25,518	$5,572	$0
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs	3,373	743
Total interest expense	24,010	5,551
Unsecured Senior Notes [Member] | Interest expense at an annual rate of 2.50% [Member]
Debt Instrument [Line Items]
Interest expense	15,981	4,808
Unsecured Senior Notes [Member] | Interest expense at an annual rate of 0.50% [Member]
Debt Instrument [Line Items]
Interest expense	1,042
Unsecured Senior Notes [Member] | Interest expense at an annual rate of 1.75% [Member]
Debt Instrument [Line Items]
Interest expense	$3,614

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Corporate Income Tax Rate [Line Items]
Income tax expense increased without tax holidays	$58,529	$43,460	$17,844
Positive impact of tax holidays on basic net income per ordinary share	$0.32	$0.24	$0.10
Hong Kong [Member] | Subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	16.50%	16.50%	16.50%
Singapore [Member] | Subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	17.00%	17.00%
Japan [Member] | Subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	25.50%	25.50%
Income tax, percentage of surcharge	2.55%	2.55%
Withholding taxes rate on remittance of dividends	20.42%
Preferential withholding taxes rate on remittance of dividends	10.00%
United States of America ("USA") [Member] | Subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
Withholding taxes rate on remittance of dividends	30.00%
United States of America ("USA") [Member] | Subsidiaries [Member] | Minimum [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	15.00%	15.00%
United States of America ("USA") [Member] | Subsidiaries [Member] | Maximum [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	39.00%	39.00%
Delaware [Member] | Subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
State income tax rate in Delaware	8.70%	8.70%
PRC [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	25.00%	25.00%	25.00%
Income tax rate under deemed-profit method	2.50%
PRC [Member] | HNTE [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	15.00%
PRC [Member] | Software Enterprise [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	12.50%
Income tax holiday, exemption period as Software Enterprise	2 years
Income taxes reduction percentage	50.00%
Income tax holiday, half rate period as Software Enterprise	3 years
PRC [Member] | Subsidiaries [Member] | Pro Forma [Member]
Corporate Income Tax Rate [Line Items]
Withholding taxes rate on remittance of dividends	10.00%
PRC [Member] | Qizhi Software [Member] | HNTE [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	15.00%	15.00%	15.00%
PRC [Member] | Beijing Qihu [Member] | HNTE [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	15.00%	15.00%	15.00%
PRC [Member] | Beijing Star World [Member] | HNTE [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	15.00%	15.00%	15.00%
PRC [Member] | Tianjin Qisi [Member] | Software Enterprise [Member]
Corporate Income Tax Rate [Line Items]
Preferential tax rate	12.50%
Income tax holiday, exemption period as Software Enterprise		2 years	2 years
PRC [Member] | Qifei Xiangyi [Member] | Software Enterprise [Member]
Corporate Income Tax Rate [Line Items]
Income tax holiday, exemption period as Software Enterprise	2 years	2 years
PRC [Member] | Other VIEs and VIEs' subsidiaries [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	25.00%
PRC [Member] | The Company and its subsidiaries, VIEs and VIEs' subsidiaries registered outside the PRC [Member] | Pro Forma [Member]
Corporate Income Tax Rate [Line Items]
Unified income tax rate	25.00%
PRC [Member] | Subsidiaries and VIEs [Member]
Corporate Income Tax Rate [Line Items]
Aggregate undistributed earnings available for distribution to the Company	651,006
Total net operating loss carry forwards	$50,874

Income_Taxes_Components_of_Inc

Income Taxes (Components of Income Tax Expense) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current and Deferred Portion of Income Tax Expense:
Current income tax expense	$69,693	$22,382	$12,062
Deferred income tax (benefit) expense	-18,268	1,041	-683
Total income tax expense	$51,425	$23,423	$11,379

Income_Taxes_Components_of_Def

Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current deferred tax assets
Accrued payroll	$5,141	$2,889
Provision of allowance for doubtful accounts	478	92
Deferred revenue-current	660	306
Less: Valuation allowance	-1,435	-158
Current deferred tax assets, net	4,844	3,129
Noncurrent deferred tax assets
Deferred revenue-noncurrent	339	383
Intangible assets	953	266
Fixed assets	100	66
Subsidy income	270	231
Net operating loss carry forwards	9,193	4,592
Promotion fee	13,894	0
Unrealized loss on available-for-sale investments	2,462	0
Less: Valuation allowance	-10,846	-4,592
Noncurrent deferred tax assets, net	16,365	946
Noncurrent deferred tax liabilities
Acquired intangible assets	8,159	2,676
Unrealized gain on available-for-sale investments	357	0
Noncurrent deferred tax liabilities	$8,516	$2,676

Income_Taxes_Effective_Income_

Income Taxes (Effective Income Tax Rate Reconciliation) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Corporate Income Tax Rate [Line Items]
Income before income tax expense	$286,494	$124,019	$62,695
Income tax expense at the statutory income tax rate	71,624	31,005	15,674
Permanent differences	5,506	1,663	870
Effect of different income tax calculation method required by tax bureau	-5	48	67
Effect of income tax holiday and preferential tax rates	-58,529	-43,460	-17,844
Changes in valuation allowance	7,855	3,758	420
Total income tax expense	51,425	23,423	11,379
PRC [Member]
Corporate Income Tax Rate [Line Items]
PRC statutory income tax rate (in percentage)	25.00%	25.00%	25.00%
Cayman Islands and other jurisdictions [Member]
Corporate Income Tax Rate [Line Items]
Effect of tax exempt status in Cayman Islands and other jurisdictions	24,701	30,241	12,217
Hong Kong [Member]
Corporate Income Tax Rate [Line Items]
Effect of different income tax rate in Hong Kong	$273	$168	($25)

Ordinary_Shares_Details

Ordinary Shares (Details) (USD $)	1 Months Ended	12 Months Ended				1 Months Ended
	Jul. 31, 2013	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Aug. 31, 2012	Jul. 31, 2012	Oct. 31, 2014	Jan. 31, 2012
Schedule of Ordinary Shares [Line Items]
Prepayment for share repurchase		$104,201,000	[1]	$0		0
Overseas internet service company [Member]
Schedule of Ordinary Shares [Line Items]
Percentage of equity interest acquired	51.00%
A related party of the Company [Member] | Overseas internet service company [Member]
Schedule of Ordinary Shares [Line Items]
Percentage of equity interest acquired	28.53%
Ordinary shares [Member]
Schedule of Ordinary Shares [Line Items]
Ordinary shares, shares authorized		500,000,000		500,000,000	500,000,000	500,000,000
Ordinary shares, par value		$0.00		$0.00	$0.00	0.001
Ordinary shares, shares issued for future delivery to employees and nonemployees		4,525,410		4,543,902	5,127,846
Ordinary shares [Member] | A related party of the Company [Member]
Schedule of Ordinary Shares [Line Items]
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)						51,722
Ordinary shares [Member] | Selling shareholder two [Member]
Schedule of Ordinary Shares [Line Items]
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)						76,372
Ordinary shares [Member] | Selling shareholder three [Member]
Schedule of Ordinary Shares [Line Items]
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)						76,372
ADS [Member]
Schedule of Ordinary Shares [Line Items]
Stock repurchase program, authorized amount									$200,000,000	$50,000,000
Stock repurchase program, number of shares repurchased but not complete legal process of registation							8,796	900
Stock repurchase program, repurchase price							$14.31	$14.50
Class A ordinary shares [Member]
Schedule of Ordinary Shares [Line Items]
Ordinary shares, shares authorized		378,000,000		378,000,000		378,000,000
Ordinary shares, par value		$0.00		$0.00		0.001
Ordinary shares, shares outstanding		147,485,168		134,123,218		134,123,218
Class B ordinary shares [Member]
Schedule of Ordinary Shares [Line Items]
Ordinary shares, shares authorized		122,000,000		122,000,000		122,000,000
Ordinary shares, par value		$0.00		$0.00		0.001
Ordinary shares, shares outstanding		45,931,163		54,767,703		54,767,703
[1]	The board of directors of the Group approved a $200 million share repurchase program in October 2014. As of December 31, 2014, the Company prepaid $104 million for the repurchase of shares. The Company completed the share repurchase program in February 2015.

Net_Income_Per_Share_Details

Net Income Per Share (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Schedule of Computation of Basic and Diluted Net Income Per Share [Line Items]
Net income attributable to Qihoo 360 Technology Co., Ltd	$222,768		$99,652		$46,746
Weighted average shares outstanding used in computing basic net income per share	185,107,216		180,476,681		176,442,866
Effect of dilutive securities:
Plus incremental weighted average ordinary shares from assumed exercise of stock options and nonvested shares using the treasury stock method	12,384,156		12,560,169		7,180,369
Weighted average shares outstanding used in computing diluted net income per share	197,491,372		193,036,850		183,623,235
Net income per Share, basic	$1.20		$0.55		$0.26
Net income per Share, diluted	$1.13		$0.52		$0.25
Class A and Class B ordinary shares [Member]
Schedule of Computation of Basic and Diluted Net Income Per Share [Line Items]
Net income attributable to Qihoo 360 Technology Co., Ltd	218,920		96,477		44,697
Weighted average shares outstanding used in computing basic net income per share	181,909,716		174,727,288		168,709,221
Effect of dilutive securities:
Weighted average shares outstanding used in computing diluted net income per share	197,491,372	[1]	193,036,850	[1]	183,623,235	[1]
Net income per Share, basic	$1.20		$0.55		$0.26
Net income per Share, diluted	$1.13		$0.52		$0.25
Participating Unvested Shares [Member]
Schedule of Computation of Basic and Diluted Net Income Per Share [Line Items]
Net income attributable to Qihoo 360 Technology Co., Ltd	3,848	[1]	3,175	[1]	2,049	[1]
Undistributed earnings allocated to participating unvested shares	$3,848	[1]	$3,175	[1]	$2,049	[1]
Weighted average shares outstanding used in computing basic net income per share	3,197,500		5,749,393		7,733,645
Effect of dilutive securities:
Net income per Share, basic	$1.20		$0.55		$0.26
[1]	The net income attributable to Qihoo 360 Technology Co. Ltd. was allocated among Class A and Class B ordinary shares, and certain nonvested shares pro rata on the basis of their right to participate in dividends.

Net_Income_Per_Share_Antidilut

Net Income Per Share (Anti-dilutive Securities Excluded) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares were excluded as their effect was anti-dilutive	244,797	533,054	4,990,513
Ordinary shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares were excluded as their effect was anti-dilutive	13,116,846	2,578,779	0

Sharebased_Compensation_Narrat

Share-based Compensation (Narrative of Share Options) (Details) (USD $)	12 Months Ended			0 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 25, 2006	Apr. 01, 2011
Share options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per option granted during period	$32.61	$13.19	$6.77
Total intrinsic value of options exercised during period	$98,112	$138,364	$19,486
Allocated share-based compensation expense	16,702	21,921	26,997
Unrecognized share-based compensation expense relating to share options	$18,875
Period for recognition of unrecognized share-based compensation expense (in years)	0 years 8 months 23 days
2006 Employee Share Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options, validity period (in years)				10 years
2006 Employee Share Option Plan [Member] | Share options [Member] | Each anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of aggregate number of options will be vested	25.00%
2011 Employee Share Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options, validity period (in years)					10 years
2011 Employee Share Incentive Plan [Member] | Share options [Member] | 12 months after start of vesting period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of aggregate number of options will be vested	20.00%
2011 Employee Share Incentive Plan [Member] | Share options [Member] | 24 months after start of vesting period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of aggregate number of options will be vested	20.00%
2011 Employee Share Incentive Plan [Member] | Share options [Member] | 36 months after start of vesting period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of aggregate number of options will be vested	30.00%
2011 Employee Share Incentive Plan [Member] | Share options [Member] | 48 months after start of vesting period [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of aggregate number of options will be vested	30.00%

Sharebased_Compensation_Fair_V

Share-based Compensation (Fair Value of Share Options, Valuation Assumptions) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (years)		6 years 4 months 6 days	6 years 4 months 6 days
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	3.96%	3.40%	2.83%
Expected life (years)	5 years 10 months 6 days
Volatility	44.28%	46.04%	46.98%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	4.61%	4.02%	3.35%
Expected life (years)	6 years 4 months 6 days
Volatility	46.02%	46.68%	74.00%

Sharebased_Compensation_Summar

Share-based Compensation (Summary of Share Options Activities) (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014
	years
Number of options
Outstanding at beginning of period	11,482,513
Granted	258,500
Exercised	-1,833,657
Expired	-3,000
Forfeited	-720,366
Outstanding at end of period	9,183,990
Vested and exercisable	4,913,833
Vested and expect to vest	16,690,231
Weighted average exercise price per option
Outstanding at beginning of period	$10.04
Granted	$45.35
Exercised	$7.96
Expired	$58.49
Forfeited	$20.23
Outstanding at end of period	$10.57
Vested and exercisable	$7
Vested and expect to vest	$8.32
Weighted average remaining contractual life (Years)
Outstanding at beginning of period	7.55
Outstanding at end of period	6.61
Vested and exercisable	6.09
Vested and expect to vest	6.28
Aggregate intrinsic value (in thousands)
Outstanding at beginning of period	$512,964
Outstanding at end of period	257,557
Vested and exercisable	153,647
Vested and expect to vest	$502,394

Sharebased_Compensation_Narrat1

Share-based Compensation (Narrative of Nonvested Shares) (Details)

1 Months Ended

12 Months Ended

1 Months Ended

23 Months Ended

12 Months Ended

In Thousands, except Share data, unless otherwise specified

Jan. 31, 2010

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Feb. 28, 2011

Feb. 28, 2011

Dec. 31, 2007

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Jan. 19, 2006

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

2006 Share Plan [Member]

USD ($)

CNY

USD ($)

USD ($)

Co-founders [Member]

Sino Honor Limited [Member]

Strengthen Goal Limited [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

Nonvested shares [Member]

USD ($)

12 months after start of vesting period [Member]

24 months after start of vesting period [Member]

36 months after start of vesting period [Member]

48 months after start of vesting period [Member]

Young Vision [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Ordinary shares allocated as equity incentive pool

18,086,101

Nonvested shares granted

2,734,139

2,734,139

1,000,000

9,951,000

Nonvested shares, shares, issued during period

3,517,544

Ordinary shares in equity pool, transferred between shareholders

11,826,000

5,550,654

Percentage of aggregate number of options will be vested

15.00%

20.00%

30.00%

35.00%

Aggregate repurchase price of nonvested shares under repurchase arrangement

1

Nonvested shares granted, repurchase arrangement

(a) in all, on or before the second anniversary of the start of vesting period; (b) 50% of otherwise vested nonvested shares, after the second anniversary but before the fourth anniversary of the start of vesting period; or (c) no shares, after the fourth anniversary of the start of vesting period.

(a) in all, on or before the second anniversary of the start of vesting period; (b) 50% of otherwise vested nonvested shares, after the second anniversary but before the fourth anniversary of the start of vesting period; or (c) no shares, after the fourth anniversary of the start of vesting period.

Allocated share-based compensation expense

$77,364

$99,166

$23,608

$57,027

Total fair value of the nonvested shares vested during period

39,476

70,980

8,361

Unrecognized share-based compensation expense relating to nonvested share

$104,592

Period for recognition of unrecognized share-based compensation expense (in years)

2 years 11 months 9 days

2 years 11 months 9 days

Sharebased_Compensation_Summar1

Share-based Compensation (Summary of Nonvested Shares Activities) (Details) (Nonvested shares [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Nonvested shares [Member]
Number of nonvested shares
Outstanding at beginning of period	10,070,794
Granted	2,734,139
Vested	-3,086,753
Forfeited	-1,174,065
Outstanding at end of period	8,544,115
Vested and to be transferred to grantees	21,503,321
Vested and expect to vest	31,574,115
Weighted average fair value per nonvested share at the grant date
Outstanding at beginning of period	$15.44
Granted	$56.27
Vested	$12.79
Forfeited	$33.32
Outstanding at end of period	$26.85

Commitments_and_Contingencies_1

Commitments and Contingencies (Operating Commitments) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating commitments, future minimum payments under commitments
2015	$27,437
2016	6,460
2017	4,061
2018	2,070
2019 and after	4,641
Total	44,669
Rental expenses under operating leases	$12,871	$5,057	$5,967

Commitments_and_Contingencies_2

Commitments and Contingencies (Other Commitments) (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Other commitments, future minimum payments under those commitments
2015	$26,644
2016	26,644
2017	26,644
2018	22,269
2019 and after	27,977
Total	$130,178

Commitments_and_Contingencies_3

Commitments and Contingencies (Group as Defendant) (Details)

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Aug. 31, 2014

Aug. 31, 2014

Oct. 31, 2012

Oct. 31, 2012

Dec. 31, 2014

Oct. 31, 2013

Oct. 31, 2013

Jan. 31, 2015

Jan. 31, 2015

Oct. 31, 2013

Oct. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

USD ($)

USD ($)

USD ($)

Unfair competitive practices and copyright infringement claim [Member]

Unfair competitive practices and copyright infringement claim [Member]

Unfair competitive practices and copyright infringement claim [Member]

Unfair competitive practices and copyright infringement claim [Member]

Unfair competitive practices and copyright infringement claim [Member]

Unfair competitive practices claim, change user default settings [Member]

Unfair competitive practices claim, change user default settings [Member]

Unfair competitive practices claim, blocking notifications of other type of software [Member]

Unfair competitive practices claim, blocking notifications of other type of software [Member]

Unfair competitive practices claim, blocking notifications of other type of software [Member]

Unfair competitive practices claim, blocking notifications of other type of software [Member]

Unfair competitive practices claim, blocking notifications of other type of software [Member]

Unfair competitive practice claim, issued pop-up notifications to block security software and made defamatory comments [Member]

Unfair competitive practice claim, issued pop-up notifications to block security software and made defamatory comments [Member]

Unfair competitive practice claim, showed negative information [Member]

Unfair competitive practice claim, showed negative information [Member]

Unfair competitive practice claim, set key words in pull-down menu of search results prompt box [Member]

Unfair competitive practice claim, set key words in pull-down menu of search results prompt box [Member]

Two affiliates of Baidu [Member]

Two affiliates of Baidu [Member]

Two affiliates of Baidu [Member]

Two affiliates of Baidu [Member]

Two affiliates of Baidu [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Two affiliates of Sogou Inc. [Member]

Baidu [Member]

Baidu [Member]

Baidu [Member]

Baidu [Member]

Baidu [Member]

Baidu [Member]

USD ($)

CNY

USD ($)

CNY

USD ($)

USD ($)

CNY

USD ($)

CNY

USD ($)

CNY

USD ($)

USD ($)

CNY

USD ($)

CNY

USD ($)

CNY

Loss Contingencies [Line Items]

Seeking value in damages

$16,100,000

100,000,000

$7,300,000

45,500,000

$8,100,000

50,000,000

$1,600,000

10,100,000

$1,600,000

10,200,000

$1,600,000

10,000,000

Awarded value as damages

100,000

500,000

800,000

5,100,000

Accrual for contingency

$900,000

$900,000

$0

$100,000

$800,000

Commitments_and_Contingencies_4

Commitments and Contingencies (Group as Plaintiff) (Details)	1 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Feb. 28, 2013	Feb. 28, 2013	Sep. 30, 2013	Sep. 30, 2013
	Defamation claim [Member]	Defamation claim [Member]	Defamation claim [Member]	Defamation claim [Member]	Unfair competitive practices claim [Member]	Unfair competitive practices claim [Member]
	Shanghai Jingwen [Member]	Shanghai Jingwen [Member]	Shanghai Jingwen [Member]	Shanghai Jingwen [Member]	Two affiliates of Sogou Inc. [Member]	Two affiliates of Sogou Inc. [Member]
	USD ($)	CNY	USD ($)	CNY	USD ($)	CNY
Gain Contingencies [Line Items]
Seeking value in damages			$8.10	50	$8.10	50
Awarded value as damages	$0.20	1.5

Segments_and_Geographic_Inform2

Segments and Geographic Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Internet services	$1,370,695	$671,088	$328,882
Others	19,965	0	150
Total revenues	1,390,660	671,088	329,032
Cost of revenues:
Internet services	-297,645	-87,838	-32,762
Others	-7,817	0	-40
Total cost of revenues	-305,462	-87,838	-32,802
Gross profit:
Internet services	1,073,050	583,250	296,120
Others	12,148	0	110
Total gross profit	1,085,198	583,250	296,230
Operating expenses:
Product development	-406,250	-255,248	-156,269
Selling and marketing	-333,701	-110,104	-58,178
General and administrative	-94,260	-117,148	-35,643
Total operating expenses	-834,211	-482,500	-250,090
Subsidy income	8,506	2,349	2,570
Income from operations	$259,493	$103,099	$48,710

Mainland_China_Contribution_Pl1

Mainland China Contribution Plan and Profit Appropriation (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Contribution Plan and Profit Appropriation [Abstract]
Provisions for full time employees benefits related to mandated contribution plan	$54,926	$31,441	$18,125
Minimum percentage of after-tax income to reserve fund before payment of dividends, required by local government	10.00%
Appropriation amount to statutory reserve funds	$21,284	$12,074	$10,408

Restricted_Net_Assets_Details

Restricted Net Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Restricted Net Assets [Line Items]
Minimum percentage of after-tax income to reserve fund before payment of dividends, required by local government	10.00%
Restricted net assets	$474,595	$261,895
Paid in capital and statutory reserves [Member] | VIEs and VIEs' Subsidiaries [Member]
Restricted Net Assets [Line Items]
Restricted net assets	246,880	89,243
Paid in capital and statutory reserves [Member] | PRC subsidiaries [Member]
Restricted Net Assets [Line Items]
Restricted net assets	$227,715	$172,652

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2015	Oct. 31, 2014	Jan. 31, 2012	Mar. 31, 2015
ADS [Member]
Subsequent Event [Line Items]
Stock repurchase program, authorized amount		$200	$50
Subsequent Event [Member] | ADS [Member]
Subsequent Event [Line Items]
Stock repurchase program, authorized amount				200
Subsequent Event [Member] | Coolpad Group Limited [Member]
Subsequent Event [Line Items]
Equity interest acquired in joint venture	45.00%
Cash consideration for acquisition	$409.05

Additional_Information_Financi2

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Balance Sheet) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
ASSETS
Cash and cash equivalents	$1,645,234	$1,013,465	$380,664	$343,731
Restricted cash	2,053	2,368
Short-term investments	58,736	748
Prepaid expenses and other current assets	221,196	80,538
Amounts due from subsidiaries and VIEs	9,799	2,871
Deferred tax assets - current	4,844	3,129
Total current assets	2,096,149	1,157,717
Acquired intangible assets, net	51,289	17,248
Long-term investments	314,979	84,293
Other noncurrent assets	97,025	39,621
Deferred tax assets - noncurrent	16,365	946
Total assets	3,331,570	1,568,896
LIABILITIES
Accrued expenses and other current liabilities	298,831	120,418
Deferred revenue-current	72,890	46,632
Amounts due to subsidiaries and VIEs	1,089	517
Total current liabilities	540,229	208,598
Deferred revenue-noncurrent	2,281	3,544
Long-term debt	1,635,000	600,000
Total liabilities	2,189,302	814,818
EQUITY
Treasury stock	-139	-139
Additional paid-in capital	669,760	568,675
Accumulated other comprehensive income (loss)	-11,772	20,380
Retained earnings	321,123	119,639
Total Qihoo 360 Technology Co. Ltd. shareholders' equity	1,028,598	736,893
TOTAL EQUITY	1,142,268	754,078	478,263	371,492
TOTAL LIABILITIES AND EQUITY	3,331,570	1,568,896
Class A ordinary shares ($0.001 par value; 378,000,000 and 378,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 134,123,218 and 147,485,168 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	147	134
Class B ordinary shares ($0.001 par value; 122,000,000 and 122,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 54,767,703 and 45,931,163 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	46	55
Parent Company [Member]
ASSETS
Cash and cash equivalents	1,242,129	695,515	220,236	241,842
Restricted cash	0	300
Short-term investments	6,839	253
Prepaid expenses and other current assets	111,872	3,206
Amounts due from subsidiaries and VIEs	459,303	167,395
Deferred tax assets - current	412	306
Total current assets	1,820,555	866,975
Acquired intangible assets, net	1,205	2,449
Investments in subsidiaries and VIEs	799,123	449,893
Long-term investments	45,211	17,139
Other noncurrent assets	26,964	11,707
Deferred tax assets - noncurrent	103	383
Total assets	2,693,161	1,348,546
LIABILITIES
Accrued expenses and other current liabilities	12,455	6,760
Deferred revenue-current	1,539	1,150
Amounts due to subsidiaries and VIEs	15,184	2,306
Total current liabilities	29,178	10,216
Deferred revenue-noncurrent	385	1,437
Long-term debt	1,635,000	600,000
Total liabilities	1,664,563	611,653
EQUITY
Treasury stock	-139	-139
Additional paid-in capital	669,760	568,675
Accumulated other comprehensive income (loss)	-11,772	20,380
Retained earnings	370,556	147,788
Total Qihoo 360 Technology Co. Ltd. shareholders' equity	1,028,598	736,893
TOTAL EQUITY	1,028,598	736,893
TOTAL LIABILITIES AND EQUITY	2,693,161	1,348,546
Parent Company [Member] | Class A ordinary shares ($0.001 par value; 378,000,000 and 378,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 134,123,218 and 147,485,168 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	147	134
Parent Company [Member] | Class B ordinary shares ($0.001 par value; 122,000,000 and 122,000,000 shares authorized as of December 31, 2013 and 2014, respectively; 54,767,703 and 45,931,163 shares issued and outstanding as of December 31, 2013 and 2014, respectively) [Member]
EQUITY
Ordinary shares	$46	$55

Additional_Information_Financi3

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Balance Sheet Parenthetical) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Class A ordinary shares [Member]
Condensed Financial Statements, Captions [Line Items]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	378,000,000	378,000,000
Ordinary shares, shares issued and outstanding	147,485,168	134,123,218
Class B ordinary shares [Member]
Condensed Financial Statements, Captions [Line Items]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	122,000,000	122,000,000
Ordinary shares, shares issued and outstanding	45,931,163	54,767,703
Parent Company [Member] | Class A ordinary shares [Member]
Condensed Financial Statements, Captions [Line Items]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	378,000,000	378,000,000
Ordinary shares, shares issued and outstanding	147,485,168	134,123,218
Parent Company [Member] | Class B ordinary shares [Member]
Condensed Financial Statements, Captions [Line Items]
Ordinary shares, par value	$0.00	$0.00
Ordinary shares, shares authorized	122,000,000	122,000,000
Ordinary shares, shares issued and outstanding	45,931,163	54,767,703

Additional_Information_Financi4

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Operations) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cost of revenues	$305,462	$87,838	$32,802
Operating expenses:
Selling and marketing	333,701	110,104	58,178
General and administrative	94,260	117,148	35,643
Product development	406,250	255,248	156,269
Total operating expenses	834,211	482,500	250,090
Loss from operations	259,493	103,099	48,710
Interest income	25,605	10,398	6,715
Interest expense	-25,518	-5,572	0
Other income	1,803	590	1,243
Exchange gain (loss)	-11,899	5,105	49
(Loss) gain in connection with short-term investments	10,230	327	-52
Gain in connection with long-term investments	26,780	11,216	2,464
Income tax expense	-51,425	-23,423	-11,379
Net income attributable to Qihoo 360 Technology Co. Ltd.	222,768	99,652	46,746
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cost of revenues	0	0	4
Operating expenses:
Selling and marketing	15,666	15,519	21,289
General and administrative	19,305	73,372	10,815
Product development	59,375	38,211	21,782
Total operating expenses	94,346	127,102	53,886
Loss from operations	-94,346	-127,102	-53,890
Interest income	20,264	6,341	4,702
Interest expense	-24,010	-5,551	0
Other income	1,447	1,197	1,277
Exchange gain (loss)	-11,520	5,100	412
(Loss) gain in connection with short-term investments	10,230	327	-52
Gain in connection with long-term investments	0	413	0
Loss before income tax expense and earnings from subsidiary and VIEs	-97,935	-119,275	-47,551
Income in earnings of subsidiaries and VIEs	321,088	219,247	94,639
Income before income tax expense	223,153	99,972	47,088
Income tax expense	-385	-320	-342
Net income attributable to Qihoo 360 Technology Co. Ltd.	$222,768	$99,652	$46,746

Additional_Information_Financi5

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Comprehensive Income) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Statement of Income Captions [Line Items]
Net income	$216,163	$97,849	$46,471
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	-17,210	11,104	2,849
Unrealized loss on available-for-sale investments	-15,876	0	0
Other comprehensive income (loss)	-33,086	11,104	2,849
Comprehensive income	183,077	108,953	49,320
Add: Comprehensive loss attributable to noncontrolling interest	7,539	1,965	277
Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.	190,616	110,918	49,597
Parent Company [Member]
Condensed Statement of Income Captions [Line Items]
Net income	222,768	99,652	46,746
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	-42,342	11,266	2,851
Unrealized loss on available-for-sale investments	10,190	0	0
Other comprehensive income (loss)	-32,152	11,266	2,851
Comprehensive income	190,616	110,918	49,597
Add: Comprehensive loss attributable to noncontrolling interest	0	0	0
Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.	$190,616	$110,918	$49,597

Additional_Information_Financi6

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Changes in Equity) (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	$754,078	$478,263	$371,492
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	1	3
Share repurchase, amount		-139
Share-based compensation	90,392	121,087	50,605
Issuance of ordinary shares in connection with business acquisitions, amount		7,864
Issuance of ordinary shares in connection with exercise of options, shares (in shares)	1,833,657
Issuance of ordinary shares in connection with exercise of options, amount	15,066	19,071	6,965
Disposal of noncontrolling interest in subsidiaries		-544	-544
Acquisition of additional equity interests in subsidiaries	-947
Net income	216,163	97,849	46,471
Other comprehensive income (loss)	-33,086	11,104	2,849
Ending Balance, amount	1,142,268	754,078	478,263
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	736,893
Net income	222,768	99,652	46,746
Other comprehensive income (loss)	-32,152	11,266	2,851
Ending Balance, amount	1,028,598	736,893
Ordinary shares [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, shares (in shares)	188,890,921	184,157,097	179,029,251
Beginning Balance, amount	189	184	179
Issuance of ordinary shares in connection with share-based compensation arrangements, shares (in shares)	2,691,753	561,517	3,512,394
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	1	3
Share repurchase, shares (in shares)		-14,544
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)		204,466
Issuance of ordinary shares in connection with exercise of options, shares (in shares)	1,833,657	3,982,385	1,615,452
Issuance of ordinary shares in connection with exercise of options, amount	2	4	2
Ending Balance, shares (in shares)	193,416,331	188,890,921	184,157,097
Ending Balance, amount	193	189	184
Ordinary shares [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, shares (in shares)	188,890,921	184,157,097	179,029,251
Beginning Balance, amount	189	184	179
Issuance of ordinary shares in connection with share-based compensation arrangements, shares (in shares)	2,691,753	561,517	3,512,394
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	1	3
Share repurchase, shares (in shares)		-14,544
Issuance of ordinary shares in connection with business acquisitions, shares (in shares)		204,466
Issuance of ordinary shares in connection with exercise of options, shares (in shares)	1,833,657	3,982,385	1,615,452
Issuance of ordinary shares in connection with exercise of options, amount	2	4	2
Ending Balance, shares (in shares)	193,416,331	188,890,921	184,157,097
Ending Balance, amount	193	189	184
Treasury Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Share repurchase, amount		-139
Ending Balance, amount	-139	-139
Treasury Stock [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Share repurchase, amount		-139
Ending Balance, amount	-139	-139
Additional Paid-in Capital [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	568,675	420,662	363,021
Share-based compensation	90,392	121,087	50,605
Issuance of ordinary shares in connection with business acquisitions, amount		7,864
Issuance of ordinary shares in connection with exercise of options, amount	15,064	19,067	6,963
Disposal of noncontrolling interest in subsidiaries		-5	73
Acquisition of additional equity interests in subsidiaries	-4,371
Ending Balance, amount	669,760	568,675	420,662
Additional Paid-in Capital [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	568,675	420,662	363,021
Share-based compensation	90,392	121,087	50,605
Issuance of ordinary shares in connection with business acquisitions, amount		7,864
Issuance of ordinary shares in connection with exercise of options, amount	15,064	19,067	6,963
Disposal of noncontrolling interest in subsidiaries		-5	73
Acquisition of additional equity interests in subsidiaries	-4,371
Ending Balance, amount	669,760	568,675	420,662
Accumulated other comprehensive income (loss) [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	20,380	9,114	6,263
Other comprehensive income (loss)	-32,152	11,266	2,851
Ending Balance, amount	-11,772	20,380	9,114
Accumulated other comprehensive income (loss) [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	20,380	9,114	6,263
Other comprehensive income (loss)	-32,152	11,266	2,851
Ending Balance, amount	-11,772	20,380	9,114
(Accumulated deficit) retained earnings [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	119,639	32,061	-4,277
Net income	222,768	99,652	46,746
Ending Balance, amount	321,123	119,639	32,061
(Accumulated deficit) retained earnings [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	147,788	48,136	1,390
Net income	222,768	99,652	46,746
Ending Balance, amount	370,556	147,788	48,136
Total Qihoo 360 Technology Co. Ltd. shareholders' equity [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	736,893	478,096	370,853
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	1	3
Share repurchase, amount		-139
Share-based compensation	90,392	121,087	50,605
Issuance of ordinary shares in connection with business acquisitions, amount		7,864
Issuance of ordinary shares in connection with exercise of options, amount	15,066	19,071	6,965
Disposal of noncontrolling interest in subsidiaries		-5	73
Acquisition of additional equity interests in subsidiaries	-4,371
Net income	222,768	99,652	46,746
Other comprehensive income (loss)	-32,152	11,266	2,851
Ending Balance, amount	1,028,598	736,893	478,096
Total Qihoo 360 Technology Co. Ltd. shareholders' equity [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, amount	736,893	478,096	370,853
Issuance of ordinary shares in connection with share-based compensation arrangements, amount	2	1	3
Share repurchase, amount		-139
Share-based compensation	90,392	121,087	50,605
Issuance of ordinary shares in connection with business acquisitions, amount		7,864
Issuance of ordinary shares in connection with exercise of options, amount	15,066	19,071	6,965
Disposal of noncontrolling interest in subsidiaries		-5	73
Acquisition of additional equity interests in subsidiaries	-4,371
Net income	222,768	99,652	46,746
Other comprehensive income (loss)	-32,152	11,266	2,851
Ending Balance, amount	$1,028,598	$736,893	$478,096

Additional_Information_Financi7

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Cash Flow) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$216,163	$97,849	$46,471
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation	95,056	121,087	50,605
Depreciation and amortization	82,531	42,629	16,457
Loss (gain) in connection with short-term investments	-10,230	-327	52
Gain in connection with long-term investments	-26,780	-11,216	-2,464
Prepaid expenses and other current assets	-19,681	-40,271	-8,404
Deferred taxes	-15,157	837	-1,204
Other noncurrent assets	184	-3,010	392
Accrued expenses and other current liabilities	67,416	53,605	23,274
Deferred revenue	5,784	20,466	10,354
Amount due from/to subsidiaries and VIEs	232	366	83
Net cash used in operating activities	380,299	210,226	117,788
Cash flows from investing activities:
(Increase) decrease in restricted cash	1,604	-431	-1,902
Purchase of intangible assets	-676	-3,068	-5,073
Purchase of short-term investments	-82,934	-997	0
Proceeds from disposal of short-term investments	41,798	762	0
Capital contribution for long-term investments	-325,000	-80,967	-24,241
Dividends received from a cost method investee	0	413	313
Net cash used in investing activities	-661,494	-196,874	-83,927
Cash flows from financing activities:
Proceeds from issuance of Convertible Senior Notes (net of issuance costs of $12,150 and $18,630 in 2013 and 2014, respectively)	1,016,370	587,850	0
Proceeds from exercise of share options	15,947	23,678	2,089
Payment for share repurchase	-104,201	0	-139
Net cash provided by financing activities	919,714	613,498	1,986
Net (decrease) increase in cash and cash equivalents	631,769	632,801	36,933
Cash and cash equivalents at beginning of year	1,013,465	380,664	343,731
Cash and cash equivalents at end of year	1,645,234	1,013,465	380,664
Parent Company [Member]
Cash flows from operating activities:
Net income	222,768	99,652	46,746
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation	89,686	121,087	50,605
Gain from investments in subsidiaries and VIEs	-321,089	-219,247	-94,639
Depreciation and amortization	1,243	1,476	582
Loss (gain) in connection with short-term investments	-10,230	-327	52
Gain in connection with long-term investments	0	-413	0
Prepaid expenses and other current assets	-3,788	463	-2,307
Deferred taxes	174	-53	-178
Other noncurrent assets	3,373	743	0
Accrued expenses and other current liabilities	5,694	5,488	149
Deferred revenue	-662	215	700
Amount due from/to subsidiaries and VIEs	-280,582	-128,738	-21,816
Net cash used in operating activities	-293,413	-119,654	-20,106
Cash flows from investing activities:
(Increase) decrease in restricted cash	300	0	-300
Purchase of intangible assets	0	-1,500	-1,500
Purchase of short-term investments	-30,025	-510	0
Proceeds from disposal of short-term investments	35,335	762	0
Capital contribution for long-term investments	-39,928	-15,760	-450
Dividends received from a cost method investee	0	413	0
Investments in subsidiaries	-53,771	0	-1,200
Net cash used in investing activities	-88,089	-16,595	-3,450
Cash flows from financing activities:
Proceeds from issuance of Convertible Senior Notes (net of issuance costs of $12,150 and $18,630 in 2013 and 2014, respectively)	1,016,370	587,850	0
Proceeds from exercise of share options	15,947	23,678	2,089
Payment for share repurchase	-104,201	0	-139
Net cash provided by financing activities	928,116	611,528	1,950
Net (decrease) increase in cash and cash equivalents	546,614	475,279	-21,606
Cash and cash equivalents at beginning of year	695,515	220,236	241,842
Cash and cash equivalents at end of year	$1,242,129	$695,515	$220,236

Additional_Information_Financi8

Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Cash Flow Parenthetical) (Details) (Convertible Senior Notes [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Debt issuance costs	$18,630	$12,150
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Debt issuance costs	$18,630	$12,150