Balance Sheet Components - Additional Information (Details) $ in Millions	1 Months Ended
Apr. 30, 2020 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Proceeds from advance payment	$ 20.5

CARES Act, Centers For Medicare And Medicaid Services, Proceeds From Advance Payment

No definition available.

Name:	cdna_CARESActCentersForMedicareAndMedicaidServicesProceedsFromAdvancePayment
Namespace Prefix:	cdna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration