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
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	$ 166,656us-gaap_AvailableForSaleSecuritiesAmortizedCost	$ 132,766us-gaap_AvailableForSaleSecuritiesAmortizedCost
Unrealized Gains	37qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax	45qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax
Unrealized Losses	(27)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax	(7)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax
Fair value	166,666us-gaap_AvailableForSaleSecuritiesCurrent	132,804us-gaap_AvailableForSaleSecuritiesCurrent
Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	76,504us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember	42,368us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Unrealized Gains	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember	1qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Unrealized Losses	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Fair value	76,504us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember	42,369us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember
Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	50,716us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember	54,810us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Unrealized Gains	10qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember	17qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Unrealized Losses	(12)qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Fair value	50,714us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember	54,827us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember
Long-Term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	39,436us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember	35,588us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Unrealized Gains	27qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember	27qlys_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	39,448us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember	35,608us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember
Cash | Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	36,024us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember	27,488us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember
Fair value	36,024us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashMember	27,488us-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	39,180us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember	183us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Unrealized Gains	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Unrealized Losses	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember
Fair value	39,180us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MoneyMarketFundsMember	183us-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	300us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Gains	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Losses	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair value	300us-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	33,280us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	4,004us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Gains	3qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	0qlys_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	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair value	33,277us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	4,004us-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	3,101us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	15,256us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Unrealized Gains	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	22qlys_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	3,099us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember	15,274us-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	1,000us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	14,697us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Gains	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	1qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Losses	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Fair value	1,000us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = us-gaap_CashAndCashEquivalentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	14,698us-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	4,998us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	32,784us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Gains	1qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	6qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Unrealized Losses	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember
Fair value	4,999us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialPaperMember	32,790us-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	12,438us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	16,894us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Gains	6qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	11qlys_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	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Fair value	12,438us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	16,905us-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	20,243us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	14,835us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember
Unrealized Gains	22qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	1qlys_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	20,255us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CorporateBondSecuritiesMember	14,833us-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		1,128us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Unrealized Gains		0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Unrealized Losses		0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_AvailableForSaleSecuritiesLineItemMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Fair value		1,128us-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	16,092us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	5,497us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Unrealized Gains	5qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	4qlys_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	0qlys_AvailableforsaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember
Fair value	$ 16,094us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember	$ 5,501us-gaap_AvailableForSaleSecuritiesCurrent / us-gaap_BalanceSheetLocationAxis = qlys_LongTermInvestmentsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember

X

- 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

X

- 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

X

- 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
Period Type:	instant

X

- Definition

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 320

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-Section 45

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