Goodwill and Intangible Assets - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017 USD ($) ReportingUnit	Mar. 31, 2016 USD ($)
Goodwill And Intangible Assets [Line Items]
Number of reporting units | ReportingUnit	2
Description of annual goodwill impairment test	On January 1, 2017, the Company adopted ASU 2017-04, which eliminated the Step 2 requirement of the goodwill impairment test. Instead, the goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. The new standard simplifies how an entity is required to test goodwill for impairment and reduces the cost and complexity of evaluating goodwill for impairment. In the three months ended March 31, 2017, the Company determined that the decrease in its market capitalization constituted an indicator of impairment and therefore a goodwill impairment test was completed as of March 31, 2017.
Goodwill impairment	$ 1,958,000	$ 0
Amortization expense of intangible assets	600,000	$ 0
Acquired in-process research and development	6,700,000
Cost of Product [Member]
Goodwill And Intangible Assets [Line Items]
Amortization expense of intangible assets	400,000
Sales and marketing [Member]
Goodwill And Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 200,000
Olerup [Member]
Goodwill And Intangible Assets [Line Items]
Description of goodwill impairment method for fair value determination	determined that the fair value of the Olerup reporting unit was $3.5 million, which was lower than its carrying value.
Fair value of reporting unit	$ 3,500,000
Goodwill impairment	$ 1,958,000
Reporting unit, discount rate	16.60%
Reporting unit, terminal growth rate	3.20%
Reporting unit, capitalization multiple	$ 7.48
Olerup [Member] | Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill impairment	2,000,000
CareDx [Member] | Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Reporting unit, amount of fair value in excess of carrying value	$ 20,000,000