v2.4.1.9

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items] |  |  |
Cash equivalents maturity, description | Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. |  |
Revenue recognition under milestone method | $ 0us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized | $ 0us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized | $ 0us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
Threshold percentage | 50.00%cdna_IncomeTaxRecognitionThresholdPercentage |  |
Laboratory, Computer, and Office Equipment [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Estimated useful lives of assets | 3 years |  |
Furniture and Fixtures [Member] |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |
Estimated useful lives of assets | 7 years |  |

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- Definition Income Tax Recognition Threshold Percentage + References No definition available. + Details
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- Definition An element designated to encapsulate any additional information related to cash and cash equivalents not otherwise addressed by the existing taxonomy. Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Definition The amount of consideration recognized during the period for the milestone or milestones. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 28 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=19771982&loc=SL6892177-166501 + Details
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