v2.4.1.9

Fair Value of Financial Instruments (Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | $ 52,014 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue | $ 69,525 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue
After One Year through Two Years | 30,681 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue | 30,107 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue
Over Two Years | 8,767 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue | 5,501 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue
Fair Value | 91,462 us-gaap_AvailableForSaleSecurities | 105,133 us-gaap_AvailableForSaleSecurities
Commercial paper |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 5,999 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 47,488 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
After One Year through Two Years | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Over Two Years | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Fair Value | 5,999 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 47,488 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
U.S. government agencies |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 33,577 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 4,004 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
After One Year through Two Years | 20,255 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 14,833 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Over Two Years | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair Value | 53,832 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 18,837 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Municipal bonds |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year |  | 1,128 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
After One Year through Two Years |  | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Over Two Years |  | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Fair Value |  | 1,128 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Corporate bonds |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 12,438 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 16,905 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
After One Year through Two Years | 3,099 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 15,274 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Over Two Years | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Fair Value | 15,537 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 32,179 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Asset-backed securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
After One Year through Two Years | 7,327 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 0 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Over Two Years | 8,767 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 5,501 qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value | $ 16,094 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | $ 5,501 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember

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