v2.4.1.9

Stock Incentive Plans - Schedule of Outstanding, Exercisable and Vested Stock Options (Detail) (USD $) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 7.36us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 1.99us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 2.67us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 3.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Options Outstanding & Exercisable, Number of Options Outstanding | 1,031,804cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions |  |  |
Options Outstanding & Exercisable, Weighted Average Remaining Contractual Life (Years) | 8 years |  |  |
Options Outstanding & Exercisable, Weighted Average Exercise Price | $ 7.36cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice |  |  |
Options Vested, Number of Options | 415,401cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber |  |  |
Number of Options vested, Weighted Average Exercise Price | $ 2.68cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice |  |  |
$0.27-0.55 [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding & Exercisable, Number of Options Outstanding | 200,002cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
Options Outstanding & Exercisable, Weighted Average Remaining Contractual Life (Years) | 7 years 9 months 18 days |  |  |
Options Outstanding & Exercisable, Weighted Average Exercise Price | $ 0.55cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
Options Vested, Number of Options | 136,560cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
Number of Options vested, Weighted Average Exercise Price | $ 0.55cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
$0.27-0.55 [Member] | Minimum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 0.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
$0.27-0.55 [Member] | Maximum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 0.55us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeOneMember |  |  |
$2.05-3.01 [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding & Exercisable, Number of Options Outstanding | 153,469cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
Options Outstanding & Exercisable, Weighted Average Remaining Contractual Life (Years) | 6 years 4 months 10 days |  |  |
Options Outstanding & Exercisable, Weighted Average Exercise Price | $ 2.78cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
Options Vested, Number of Options | 147,641cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
Number of Options vested, Weighted Average Exercise Price | $ 2.77cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
$2.05-3.01 [Member] | Minimum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 2.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
$2.05-3.01 [Member] | Maximum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 3.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeTwoMember |  |  |
$3.36-3.97 [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding & Exercisable, Number of Options Outstanding | 110,188cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
Options Outstanding & Exercisable, Weighted Average Remaining Contractual Life (Years) | 3 years 6 months 18 days |  |  |
Options Outstanding & Exercisable, Weighted Average Exercise Price | $ 3.47cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
Options Vested, Number of Options | 110,188cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
Number of Options vested, Weighted Average Exercise Price | $ 3.47cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
$3.36-3.97 [Member] | Minimum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 3.36us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
$3.36-3.97 [Member] | Maximum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 3.97us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeThreeMember |  |  |
$7.03-12.40 [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding & Exercisable, Number of Options Outstanding | 568,145cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |
Options Outstanding & Exercisable, Weighted Average Remaining Contractual Life (Years) | 9 years 4 months 17 days |  |  |
Options Outstanding & Exercisable, Weighted Average Exercise Price | $ 11.75cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |
Options Vested, Number of Options | 21,012cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |
Number of Options vested, Weighted Average Exercise Price | $ 11.82cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |
$7.03-12.40 [Member] | Minimum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 7.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |
$7.03-12.40 [Member] | Maximum [Member] |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding, Range of Exercise Prices | $ 12.40us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = cdna_ExercisePriceRangeFourMember |  |  |

X
- Definition Share based compensation arrangement by share based payment award options vested outstanding number. + References No definition available. + Details
Name: | cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedOutstandingNumber
Namespace Prefix: | cdna_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based compensation arrangement by share based payment award options vested weighted average exercise price. + References No definition available. + Details
Name: | cdna_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice
Namespace Prefix: | cdna_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share based compensation shares authorized under stock option plans exercise price range number of outstanding and exercisable options. + References No definition available. + Details
Name: | cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptions
Namespace Prefix: | cdna_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based compensation shares authorized under stock option plans exercise price range number of outstanding and exercisable options weighted average exercise price. + References No definition available. + Details
Name: | cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageExercisePrice
Namespace Prefix: | cdna_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based compensation shares authorized under stock option plans exercise price range number of outstanding and exercisable options weighted average remaining contractual term. + References No definition available. + Details
Name: | cdna_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingAndExercisableOptionsWeightedAverageRemainingContractualTerm
Namespace Prefix: | cdna_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=cdna_ExercisePriceRangeFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=cdna_ExercisePriceRangeOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=cdna_ExercisePriceRangeThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=cdna_ExercisePriceRangeTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |