v2.4.1.9

Balance Sheet Components - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Balance Sheet Components [Line Items] |  |  |
Depreciation and amortization expense | $ 512,000us-gaap_DepreciationDepletionAndAmortization | $ 663,000us-gaap_DepreciationDepletionAndAmortization | $ 1,072,000us-gaap_DepreciationDepletionAndAmortization
Accumulated amortization | 11,092,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment | 10,902,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment |
Amortization expense, included in depreciation and amortization expense | 59,000us-gaap_AdjustmentForAmortization | 26,000us-gaap_AdjustmentForAmortization | 70,000us-gaap_AdjustmentForAmortization
Laboratory equipment and computer and office equipment [Member] |  |  |
Balance Sheet Components [Line Items] |  |  |
Assets purchased under capital leases | 1,631,000us-gaap_CapitalLeasedAssetsGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cdna_LaboratoryComputerAndOfficeEquipmentMember | 1,439,000us-gaap_CapitalLeasedAssetsGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cdna_LaboratoryComputerAndOfficeEquipmentMember |
Accumulated amortization | $ 1,473,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cdna_LaboratoryComputerAndOfficeEquipmentMember | $ 1,414,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cdna_LaboratoryComputerAndOfficeEquipmentMember |

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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 14 -Article 5 + Details
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- Definition The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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- Definition Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735 + Details
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Balance Type: | debit
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- Definition The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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