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Common Stock and Preferred Stock - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
vote_per_share
Dec. 31, 2013
Dec. 31, 2012
Jun. 25, 2013
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   8,631,427us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities 8,631,427us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities  
Each share of common stock is entitled to vote 1nstg_CommonStockVotesPerShare1      
Preferred stock, shares authorized 15,000,000us-gaap_PreferredStockSharesAuthorized 15,000,000us-gaap_PreferredStockSharesAuthorized    
Preferred stock, shares issued 0us-gaap_PreferredStockSharesIssued 0us-gaap_PreferredStockSharesIssued    
Preferred stock, shares outstanding 0us-gaap_PreferredStockSharesOutstanding     0us-gaap_PreferredStockSharesOutstanding
Accretion of mandatorily redeemable convertible preferred stock $ 0us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment $ 4,653us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment $ 7,533us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment  
Preferred Stock, redemption rate 8.00%nstg_PreferredStockRedemptionPricePercentageOfIssuePrice      
Preferred stock warrants were converted into warrants to purchase common stock 572,496nstg_ConversionOfPreferredStockWarrantsToCommonStockWarrantsShares      
Exercise price of common stock warrants $ 8.77nstg_ExercisePriceOfCommonStockWarrants      
Series A Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   (557,339)us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember		    
Preferred stock converted into common stock on a basis     1.403030-for-one basis  
Series B Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   (515,836)us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember		    
Preferred stock converted into common stock on a basis     1.559429-for-one basis  
Series C Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   (3,551,060)us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember		    
Preferred stock converted into common stock on a basis     One-for-one basis  
Series D Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   (2,430,054)us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		    
Preferred stock converted into common stock on a basis     One-for-one basis  
Series E Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Conversion of Convertible Preferred Stock Into Common Stock, Shares   (1,063,951)us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesEPreferredStockMember		    
Preferred stock converted into common stock on a basis     One-for-one basis  
Mandatorily Redeemable Convertible Preferred Stock [Member]        
Common And Preferred Stock [Line Items]        
Redemption terms At any time after November 29, 2017 and upon 30 day notice from the holders of 65% of the outstanding Preferred Stock      
Preferred stock, redemption date Nov. 29, 2017      
Preferred stock, redemption notice period 30 days      
Holders outstanding preferred stock 65.00%nstg_PercentageOfOutstandingPreferredShareholdersVoteRequiredForConversion
/ us-gaap_ScheduleOfSharesSubjectToMandatoryRedemptionBySettlementTermsAxis
= us-gaap_ConvertiblePreferredStockSubjectToMandatoryRedemptionMember