v2.4.1.9

Warrants - Components of Common Stock Warrants Outstanding (Detail) (Common Stock [Member], USD $)	12 Months Ended
	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Number of Shares Outstanding Underlying Warrants	82,190us-gaap_ClassOfWarrantOrRightOutstanding
Class Of Warrant Or Right Issued on July 2006 [Member]
Class of Warrant or Right [Line Items]
Issue Date	2006-07
Original Term	10 years
Exercise Price	$ 31.72us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1 / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateFourMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Number of Shares Outstanding Underlying Warrants	17,656us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateFourMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Class Of Warrant Or Right Issued on November 2006 [Member]
Class of Warrant or Right [Line Items]
Issue Date	2006-11
Original Term	10 years
Exercise Price	$ 31.72us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1 / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateFiveMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Number of Shares Outstanding Underlying Warrants	1,576us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateFiveMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Class Of Warrant Or Right Issued on February 2008 [Member]
Class of Warrant or Right [Line Items]
Issue Date	2008-02
Original Term	10 years
Exercise Price	$ 35.07us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1 / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateSixMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Number of Shares Outstanding Underlying Warrants	22,792us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateSixMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Class Of Warrant Or Right Issued on August 2009 [Member]
Class of Warrant or Right [Line Items]
Issue Date	2009-08
Original Term	10 years
Exercise Price	$ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1 / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateSevenMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Number of Shares Outstanding Underlying Warrants	33,472us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateSevenMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Class Of Warrant Or Right Issued on July 2010 [Member]
Class of Warrant or Right [Line Items]
Issue Date	2010-07
Original Term	9 years
Exercise Price	$ 21.78us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1 / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateEightMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Number of Shares Outstanding Underlying Warrants	6,694us-gaap_ClassOfWarrantOrRightOutstanding / us-gaap_ClassOfWarrantOrRightAxis = cdna_ClassOfWarrantOrRightIssuedDateEightMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember

X

- Definition

Class of warrant or right warrant issuance month and year.

+ References

No definition available.

+ Details

Name:	cdna_ClassOfWarrantOrRightWarrantIssuanceMonthAndYear
Namespace Prefix:	cdna_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(i)(4))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_ClassOfWarrantOrRightLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph i

-Article 4

+ Details

Name:	us-gaap_ClassOfWarrantOrRightOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration