Additional Information - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Statement of Income Captions [Line Items]
Net income	$ 216,163us-gaap_ProfitLoss	$ 97,849us-gaap_ProfitLoss	$ 46,471us-gaap_ProfitLoss
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.	190,616us-gaap_ComprehensiveIncomeNetOfTax	110,918us-gaap_ComprehensiveIncomeNetOfTax	49,597us-gaap_ComprehensiveIncomeNetOfTax
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 - Financial Statement Schedule I Condensed Financial Information of Parent Company (Condensed Statements of Comprehensive Income) (Details) (USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Condensed Statement of Income Captions [Line Items]

Net income

$ 216,163us-gaap_ProfitLoss

$ 97,849us-gaap_ProfitLoss

$ 46,471us-gaap_ProfitLoss

Other comprehensive income (loss), net of tax:

Foreign currency translation adjustments

(17,210)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

11,104us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

2,849us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax

Unrealized loss on available-for-sale investments

(15,876)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax

0us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax

Other comprehensive income (loss)

(33,086)us-gaap_OtherComprehensiveIncomeLossNetOfTax

11,104us-gaap_OtherComprehensiveIncomeLossNetOfTax

2,849us-gaap_OtherComprehensiveIncomeLossNetOfTax

Comprehensive income

183,077us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

108,953us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

49,320us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

Add: Comprehensive loss attributable to noncontrolling interest

7,539us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

1,965us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

277us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest

Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.

190,616us-gaap_ComprehensiveIncomeNetOfTax

110,918us-gaap_ComprehensiveIncomeNetOfTax

49,597us-gaap_ComprehensiveIncomeNetOfTax

Parent Company [Member]

Condensed Statement of Income Captions [Line Items]

Net income

222,768us-gaap_ProfitLoss
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99,652us-gaap_ProfitLoss
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46,746us-gaap_ProfitLoss
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Other comprehensive income (loss), net of tax:

Foreign currency translation adjustments

(42,342)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
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11,266us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
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2,851us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
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Unrealized loss on available-for-sale investments

10,190us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
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0us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
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Other comprehensive income (loss)

(32,152)us-gaap_OtherComprehensiveIncomeLossNetOfTax
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11,266us-gaap_OtherComprehensiveIncomeLossNetOfTax
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2,851us-gaap_OtherComprehensiveIncomeLossNetOfTax
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Comprehensive income

190,616us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
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110,918us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
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49,597us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
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Add: Comprehensive loss attributable to noncontrolling interest

0us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest
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= us-gaap_ParentCompanyMember

Comprehensive income attributable to Qihoo 360 Technology Co. Ltd.

$ 190,616us-gaap_ComprehensiveIncomeNetOfTax
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= us-gaap_ParentCompanyMember

$ 110,918us-gaap_ComprehensiveIncomeNetOfTax
/ dei_LegalEntityAxis
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$ 49,597us-gaap_ComprehensiveIncomeNetOfTax
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember

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