v2.4.1.9

Fair Value of Financial Instruments (Cash and Cash Equivalents, Available-for-sale Securities, Restricted Cash Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | $ 166,656 us-gaap_AvailableForSaleSecuritiesAmortizedCost | $ 132,766 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Unrealized Gains | 37 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax | 45 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax
Unrealized Losses | (27)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax | (7)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax
Fair value | 166,666 us-gaap_AvailableForSaleSecuritiesCurrent | 132,804 us-gaap_AvailableForSaleSecuritiesCurrent
Cash and Cash Equivalents |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 76,504 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember | 42,368 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Unrealized Gains | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember | 1 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Unrealized Losses | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Fair value | 76,504 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember | 42,369 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Short-term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 50,716 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember | 54,810 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Unrealized Gains | 10 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember | 17 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Unrealized Losses | (12)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Fair value | 50,714 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember | 54,827 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Long-Term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 39,436 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember | 35,588 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Unrealized Gains | 27 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember | 27 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Unrealized Losses | (15)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember | (7)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Fair value | 39,448 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember | 35,608 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Cash | Cash and Cash Equivalents |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 36,024 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember | 27,488 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember
Fair value | 36,024 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember | 27,488 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember
Money market funds | Cash and Cash Equivalents |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 39,180 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember | 183 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Unrealized Gains | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Unrealized Losses | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Fair value | 39,180 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember | 183 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
U.S. government agencies | Cash and Cash Equivalents |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 300 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember |
Unrealized Gains | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember |
Unrealized Losses | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember |
Fair value | 300 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember |
U.S. government agencies | Short-term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 33,280 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 4,004 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Gains | 3 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Losses | (6)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair value | 33,277 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 4,004 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
U.S. government agencies | Long-Term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 3,101 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 15,256 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Gains | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 22 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Losses | (2)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | (4)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair value | 3,099 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 15,274 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Commercial paper | Cash and Cash Equivalents |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 1,000 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 14,697 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Gains | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 1 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Losses | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Fair value | 1,000 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 14,698 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Commercial paper | Short-term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 4,998 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 32,784 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Gains | 1 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 6 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Losses | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Fair value | 4,999 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember | 32,790 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Corporate bonds | Short-term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 12,438 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 16,894 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Gains | 6 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 11 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Losses | (6)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Fair value | 12,438 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 16,905 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Corporate bonds | Long-Term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 20,243 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 14,835 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Gains | 22 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 1 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Losses | (10)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | (3)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Fair value | 20,255 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember | 14,833 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Municipal bonds | Short-term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total |  | 1,128 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Unrealized Gains |  | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Unrealized Losses |  | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Fair value |  | 1,128 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Asset-backed securities | Long-Term Investments |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Amortized cost, total | 16,092 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 5,497 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Gains | 5 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 4 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Losses | (3)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 0 qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair value | $ 16,094 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | $ 5,501 us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
Name: | qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax
Namespace Prefix: | qlys_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
Name: | qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax
Namespace Prefix: | qlys_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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