v2.4.1.9
Debt - Additional Information (Detail) (USD $)
0 Months Ended 1 Months Ended 3 Months Ended 12 Months Ended 1 Months Ended
Jul. 22, 2014
Aug. 31, 2012
Jul. 22, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Apr. 30, 2012
Debt_Instruments
Apr. 17, 2014
Dec. 31, 2011
Aug. 31, 2013
Debt Instrument [Line Items]                    
Loan and security agreement cost   $ 15,000,000us-gaap_DebtInstrumentFaceAmount                
Total repayment of principal   10,333,833us-gaap_DebtInstrumentPeriodicPaymentPrincipal                
Termination fee paid   875,000cdna_DebtInstrumentTerminationFeeAmount                
Interest expense           628,000us-gaap_InterestExpenseDebt        
Net cash proceeds from loan   3,432,260us-gaap_ProceedsFromIssuanceOfDebt                
Loan deferral additional fee       150,000us-gaap_DebtInstrumentCollateralFee            
Loan to defer the beginning of principal repayment       Mar. 01, 2014            
Interest payment       566,822us-gaap_DebtInstrumentPeriodicPayment            
Annual interest rate       9.95%us-gaap_DebtInstrumentInterestRateStatedPercentage            
Final payment due at the end of the term       1,275,000us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid            
Facility Fee amount       75,000us-gaap_DebtInstrumentFeeAmount            
Loan interest description       Interest-only payments for 18 months followed by 30 equal monthly principal and interest payments            
Estimated fair value of warrants       (1,464,000)us-gaap_FairValueAdjustmentOfWarrants 525,000us-gaap_FairValueAdjustmentOfWarrants (2,000)us-gaap_FairValueAdjustmentOfWarrants        
Initial Public offering, closing date       Jul. 22, 2014            
Shares issued upon conversion 510,777us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities                  
Amortization of debt discount     256,000cdna_AmortizationOfDebtDiscount              
Extinguishment of embedded derivative       120,000us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability            
Illumina, Inc. [Member]                    
Debt Instrument [Line Items]                    
Annual interest rate               8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ dei_LegalEntityAxis
= cdna_IlluminaIncMember
   
Subordinated convertible promissory note issued               5,000,000us-gaap_ConvertibleSubordinatedDebt
/ dei_LegalEntityAxis
= cdna_IlluminaIncMember
   
Subordinated convertible promissory note maturity term       1 year            
Subordinated Convertible Promissory Notes [Member]                    
Debt Instrument [Line Items]                    
Annual interest rate                 7.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_ShortTermDebtTypeAxis
= cdna_SubordinatedConvertiblePromissoryNotesMember
 
Principal amount of notes                 11,365,000cdna_ConvertibleSubordinatedNotesPrincipalAmount
/ us-gaap_ShortTermDebtTypeAxis
= cdna_SubordinatedConvertiblePromissoryNotesMember
 
Amortization of debt discount           39,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_ShortTermDebtTypeAxis
= cdna_SubordinatedConvertiblePromissoryNotesMember
       
Series G Convertible Preferred Stock [Member]                    
Debt Instrument [Line Items]                    
Warrants to purchase stock of convertible preferred stock, shares             357,216us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
     
Warrants to purchase stock of convertible preferred stock, per share             $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
     
Principal and interest amount of notes             12,423,000us-gaap_ConvertibleNotesPayable
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
     
Convertible notes, shares             570,294us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
     
Convertible notes, per share             $ 21.78us-gaap_DebtInstrumentConvertibleConversionPrice1
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
     
2012 Loan [Member] | Series G Convertible Preferred Stock [Member]                    
Debt Instrument [Line Items]                    
Warrants to purchase stock of convertible preferred stock, shares                   167,182us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandTwelveTermLoanMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
Warrants to purchase stock of convertible preferred stock, per share                   $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandTwelveTermLoanMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
Warrants exercisable period       The warrants are exercisable until 2019            
2010 Loan [Member]                    
Debt Instrument [Line Items]                    
Amortization expense           4,400us-gaap_AmortizationOfFinancingCosts
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandAndTenTermLoanMember
       
2010 Loan [Member] | Series G Convertible Preferred Stock [Member]                    
Debt Instrument [Line Items]                    
Warrants to purchase stock of convertible preferred stock, shares       17,215us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandAndTenTermLoanMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
           
Warrants to purchase stock of convertible preferred stock, per share       $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandAndTenTermLoanMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember
           
Warrants exercisable period       The warrants were exercisable until 2017            
Estimated fair value of warrants       $ 8,000us-gaap_FairValueAdjustmentOfWarrants
/ us-gaap_LongtermDebtTypeAxis
= cdna_TwoThousandAndTenTermLoanMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember