v2.4.1.9

Income Taxes (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax [Line Items]
Valuation allowance increase (decrease)										$ 900,000us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Valuation allowance	3,079,000us-gaap_DeferredTaxAssetsValuationAllowance				27,181,000us-gaap_DeferredTaxAssetsValuationAllowance				3,079,000us-gaap_DeferredTaxAssetsValuationAllowance	27,181,000us-gaap_DeferredTaxAssetsValuationAllowance
Provision for (benefit from) income taxes	(22,270,000)us-gaap_IncomeTaxExpenseBenefit	283,000us-gaap_IncomeTaxExpenseBenefit	174,000us-gaap_IncomeTaxExpenseBenefit	182,000us-gaap_IncomeTaxExpenseBenefit	128,000us-gaap_IncomeTaxExpenseBenefit	210,000us-gaap_IncomeTaxExpenseBenefit	92,000us-gaap_IncomeTaxExpenseBenefit	70,000us-gaap_IncomeTaxExpenseBenefit	(21,631,000)us-gaap_IncomeTaxExpenseBenefit	500,000us-gaap_IncomeTaxExpenseBenefit	358,000us-gaap_IncomeTaxExpenseBenefit
Undistributed earnings of foreign subsidiaries	6,800,000us-gaap_UndistributedEarningsOfForeignSubsidiaries				8,500,000us-gaap_UndistributedEarningsOfForeignSubsidiaries				6,800,000us-gaap_UndistributedEarningsOfForeignSubsidiaries	8,500,000us-gaap_UndistributedEarningsOfForeignSubsidiaries
Unrecognized tax benefits that would impact effective tax rate	2,100,000us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate				1,000,000us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate				2,100,000us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1,000,000us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1,000,000us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Internal Revenue Service (IRS) [Member]
Income Tax [Line Items]
Operating loss carryforwards	56,700,000us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember								56,700,000us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember
Deferred tax asset not recognized, net operating loss carryforwards	21,400,000qlys_DeferredTaxAssetNotRecognizedNetOperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember								21,400,000qlys_DeferredTaxAssetNotRecognizedNetOperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember
Internal Revenue Service (IRS) [Member] | Research and Development Credits [Member]
Income Tax [Line Items]
Tax credit carryforward	5,000,000us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember								5,000,000us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_InternalRevenueServiceIRSMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Valuation allowance	3,079,000us-gaap_DeferredTaxAssetsValuationAllowance / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember								3,079,000us-gaap_DeferredTaxAssetsValuationAllowance / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember
Operating loss carryforwards	10,500,000us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember								10,500,000us-gaap_OperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember
Deferred tax asset not recognized, net operating loss carryforwards	1,700,000qlys_DeferredTaxAssetNotRecognizedNetOperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember								1,700,000qlys_DeferredTaxAssetNotRecognizedNetOperatingLossCarryforwards / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember
State and Local Jurisdiction [Member] | Research and Development Credits [Member]
Income Tax [Line Items]
Tax credit carryforward	5,200,000us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember								5,200,000us-gaap_TaxCreditCarryforwardAmount / us-gaap_IncomeTaxAuthorityAxis = us-gaap_StateAndLocalJurisdictionMember / us-gaap_TaxCreditCarryforwardAxis = us-gaap_ResearchMember
Federal and State Jurisdictions [Member]
Income Tax [Line Items]
Provision for (benefit from) income taxes	$ (23,700,000)us-gaap_IncomeTaxExpenseBenefit / us-gaap_IncomeTaxAuthorityAxis = us-gaap_DomesticCountryMember

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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