v2.4.1.9
Warrants - Components of Convertible Preferred Stock Warrants Outstanding (Detail) (Series G Convertible Preferred Stock [Member], USD $)
In Thousands, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Apr. 30, 2012
Class of Warrant or Right [Line Items]    
Exercise Price   $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Number of Shares of Outstanding Underlying Warrant 541,613us-gaap_ClassOfWarrantOrRightOutstanding  
Estimated Fair Value as of December 31, 2013 $ 525us-gaap_WarrantsNotSettleableInCashFairValueDisclosure  
Class Of Warrant Or Right Issued Date One [Member]
    
Class of Warrant or Right [Line Items]    
Issue Date 2010-12  
Original Term 7 years  
Exercise Price $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateOneMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Number of Shares of Outstanding Underlying Warrant 17,215us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateOneMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Estimated Fair Value as of December 31, 2013 14us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateOneMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Class Of Warrant Or Right Issued Date Two [Member]
    
Class of Warrant or Right [Line Items]    
Issue Date 2012-04  
Original Term 5 years  
Exercise Price $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateTwoMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Number of Shares of Outstanding Underlying Warrant 357,216us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateTwoMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Estimated Fair Value as of December 31, 2013 218us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateTwoMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Class Of Warrant Or Right Issued Date Three [Member]
    
Class of Warrant or Right [Line Items]    
Issue Date 2012-08  
Original Term 7 years  
Exercise Price $ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateThreeMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Number of Shares of Outstanding Underlying Warrant 167,182us-gaap_ClassOfWarrantOrRightOutstanding
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateThreeMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember		  
Estimated Fair Value as of December 31, 2013 $ 293us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
/ us-gaap_ClassOfWarrantOrRightAxis
= cdna_ClassOfWarrantOrRightIssuedDateThreeMember
/ us-gaap_StatementClassOfStockAxis
= cdna_SeriesGConvertiblePreferredStockMember