v2.4.1.9

Income Taxes - Schedule of Reconciliation of Difference between Benefit for Income Taxes and Income Taxes at Statutory U.S. Federal Income Tax Rate (Detail) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation and Amortization, Percent [Abstract] |  |  |
Federal tax at statutory rate | 34.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate | 34.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate | 34.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Stock based compensation | (9.50%)us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost | (11.40%)us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost | 0.00%us-gaap_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost
Change in valuation allowance | 190.60%us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance | (8.60%)us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance | (30.90%)us-gaap_EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance
Change in unrecognized tax benefits | 0.00%cdna_EffectiveIncomeTaxRateReconciliationChangeInUnrecognizedTaxBenefits | (8.40%)cdna_EffectiveIncomeTaxRateReconciliationChangeInUnrecognizedTaxBenefits | 0.00%cdna_EffectiveIncomeTaxRateReconciliationChangeInUnrecognizedTaxBenefits
Preferred stock warrant revaluation | (0.70%)cdna_EffectiveIncomeTaxRateReconciliationPreferredStockWarrantRevaluation | (5.00%)cdna_EffectiveIncomeTaxRateReconciliationPreferredStockWarrantRevaluation | 0.00%cdna_EffectiveIncomeTaxRateReconciliationPreferredStockWarrantRevaluation
Interest expense | (5.80%)cdna_EffectiveIncomeTaxRateReconciliationInterestExpense | 0.00%cdna_EffectiveIncomeTaxRateReconciliationInterestExpense | (2.30%)cdna_EffectiveIncomeTaxRateReconciliationInterestExpense
Contingent liability for IMX acquisition | 38.20%cdna_EffectiveIncomeTaxRateReconciliationLiabilityContingentForUnconsolidatedSubsidiaryPercent | 0.00%cdna_EffectiveIncomeTaxRateReconciliationLiabilityContingentForUnconsolidatedSubsidiaryPercent | 0.00%cdna_EffectiveIncomeTaxRateReconciliationLiabilityContingentForUnconsolidatedSubsidiaryPercent
IMX acquisition costs | (36.70%)cdna_EffectiveIncomeTaxRateReconciliationAcquisitionCosts | 0.00%cdna_EffectiveIncomeTaxRateReconciliationAcquisitionCosts | 0.00%cdna_EffectiveIncomeTaxRateReconciliationAcquisitionCosts
Other | (1.30%)us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments | (0.60%)us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments | (0.80%)us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments
Effective income tax rate | 208.80%us-gaap_EffectiveIncomeTaxRateContinuingOperations | 0.00%us-gaap_EffectiveIncomeTaxRateContinuingOperations | 0.00%us-gaap_EffectiveIncomeTaxRateContinuingOperations

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- Definition Effective income tax rate reconciliation acquisition costs. + References No definition available. + Details
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- Definition Effective income tax rate reconciliation change in unrecognized tax benefits. + References No definition available. + Details
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- Definition Effective income tax rate reconciliation interest expense. + References No definition available. + Details
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- Definition Effective income tax rate reconciliation, Liability contingent for unconsolidated subsidiary, percent. + References No definition available. + Details
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- Definition Effective income tax rate reconciliation, preferred stock warrant revaluation. + References No definition available. + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 Reference 3: 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.(h)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Subparagraph 2 -Article 4 + Details
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 + Details
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- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 + Details
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- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to equity-based compensation costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 + Details
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- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319 + Details
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