v2.4.1.9
The Company and Summary of Significant Accounting Policies (Details)
 0 Months Ended 3 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended
Oct. 03, 2012
USD ($)
Sep. 30, 2012
Dec. 31, 2014
USD ($)
contract
Dec. 31, 2013
USD ($)
contract
Dec. 31, 2012
USD ($)
Dec. 31, 2014
Minimum
Dec. 31, 2014
Maximum
Dec. 31, 2014
Scanner appliances
Dec. 31, 2014
Forward contracts
USD ($)
Dec. 31, 2013
Forward contracts
USD ($)
Dec. 31, 2014
Forward contracts
EUR (€)
Dec. 31, 2014
Forward contracts
GBP (£)
Dec. 31, 2013
Forward contracts
EUR (€)
Dec. 31, 2013
Forward contracts
GBP (£)
Dec. 31, 2014
Customer concentration risk
Accounts receivable
customer
Dec. 31, 2013
Customer concentration risk
Accounts receivable
customer
Oct. 03, 2012
Common Stock
Dec. 31, 2012
Common Stock
Dec. 31, 2014
Software and software development costs
USD ($)
Dec. 31, 2013
Software and software development costs
USD ($)
Oct. 03, 2012
Convertible Preferred Stock
USD ($)
Oct. 03, 2012
IPO
Common Stock
USD ($)
Oct. 03, 2012
IPO
Convertible Preferred Stock
Oct. 03, 2012
IPO Overallotment
Common Stock
Initial Public Offering                                                
Shares sold in IPO, including existing shares                                           8,711,250qlys_SharesSoldInInitialPublicOfferingIncludingExistingShares
/ qlys_OfferingSourceAxis
= us-gaap_IPOMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember		    
Shares sold in initial public offering, including existing shares, price per share                                           $ 12.00qlys_SharesSoldInInitialPublicOfferingIncludingExistingSharesPricePerShare
/ qlys_OfferingSourceAxis
= us-gaap_IPOMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember		    
Issuance of common stock upon initial public offering, net of offering costs (in shares)                                 7,836,250us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		 7,836,250us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		           1,136,250us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ qlys_OfferingSourceAxis
= qlys_IpoOverallotmentMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
Shares sold by existing stockholders during initial public offering                                           875,000qlys_SharesSoldByExistingStockholdersDuringInitialPublicOffering
/ qlys_OfferingSourceAxis
= us-gaap_IPOMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember		    
Proceeds from issuance of initial public offering $ 87,500,000us-gaap_ProceedsFromIssuanceInitialPublicOffering                                              
Sale of stock, expenses incurred in offering 2,900,000qlys_SaleOfStockExpensesIncurredInOffering                                              
Conversion of stock, shares converted                                             17,597,258us-gaap_ConversionOfStockSharesConverted1
/ qlys_OfferingSourceAxis
= us-gaap_IPOMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_ConvertiblePreferredStockMember		  
Concentration of Credit Risk                                                
Concentration risk, number of customers                             0qlys_ConcentrationRiskNumberOfCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 0qlys_ConcentrationRiskNumberOfCustomers
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		                
Property Equipment, Net                                                
Property, plant and equipment, useful life           3 years 5 years 3 years                                
Goodwill and Intangible Assets                                                
Finite-lived intangible asset, useful life           3 years 14 years                                  
Software Development Costs                                                
Capitalized software development costs     98,000qlys_CapitalizedSoftwareDevelopmentCosts 0qlys_CapitalizedSoftwareDevelopmentCosts 0qlys_CapitalizedSoftwareDevelopmentCosts                                      
Capitalized development costs     3,469,000us-gaap_FiniteLivedIntangibleAssetsGross                               400,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_SoftwareAndSoftwareDevelopmentCostsMember		 300,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_SoftwareAndSoftwareDevelopmentCostsMember		        
Accumulated Amortization     1,763,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization 1,370,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization                             300,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_SoftwareAndSoftwareDevelopmentCostsMember		          
Derivative Financial Instruments                                                
Derivative, number of instruments held     2us-gaap_DerivativeNumberOfInstrumentsHeld 2us-gaap_DerivativeNumberOfInstrumentsHeld                                        
Derivative, notional amount                     6,000,000invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		 2,100,000invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		 6,300,000invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		 2,000,000invest_DerivativeNotionalAmount
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		                    
Foreign currency contract, asset, fair value disclosure     0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure 0us-gaap_ForeignCurrencyContractAssetFairValueDisclosure                                        
Derivative instruments not designated as hedging instruments, gain                 700,000us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGain
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		                              
Foreign currency transaction loss, before tax     (1,400,000)us-gaap_ForeignCurrencyTransactionLossBeforeTax                                          
Derivative instruments not designated as hedging instruments, loss                   800,000us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLoss
/ us-gaap_DerivativeByNatureAxis
= us-gaap_ForwardContractsMember		                            
Foreign currency transaction gain, before tax       200,000us-gaap_ForeignCurrencyTransactionGainBeforeTax                                        
Advertising Expenses                                                
Advertising expense     5,300,000us-gaap_AdvertisingExpense 4,200,000us-gaap_AdvertisingExpense 4,300,000us-gaap_AdvertisingExpense                                      
Reverse Stock Split                                                
Stockholders' equity, reverse stock split   one-for-ten reverse stock split                                            
Stockholders' equity note, stock split, conversion ratio   0.1us-gaap_StockholdersEquityNoteStockSplitConversionRatio1                                            
Foreign exchange losses     (664,000)us-gaap_ForeignCurrencyTransactionGainLossBeforeTax (679,000)us-gaap_ForeignCurrencyTransactionGainLossBeforeTax (238,000)us-gaap_ForeignCurrencyTransactionGainLossBeforeTax                                      
Conversion of Stock, Amount Converted     $ 0us-gaap_ConversionOfStockAmountConverted1 $ 0us-gaap_ConversionOfStockAmountConverted1 $ 63,873,000us-gaap_ConversionOfStockAmountConverted1                               $ 63,900,000us-gaap_ConversionOfStockAmountConverted1
/ us-gaap_StatementClassOfStockAxis
= us-gaap_ConvertiblePreferredStockMember