Goodwill and Intangible Assets - Summary of Goodwill (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Indefinite Lived Intangible Assets By Major Class [Line Items]
Balance as of December 31, 2015	$ 12,005
Goodwill acquired	16,786
Foreign currency translation adjustments	(719)
Balance as of June 30, 2016	28,072
CareDx [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Balance as of December 31, 2015	12,005
Goodwill acquired	0
Foreign currency translation adjustments	0
Balance as of June 30, 2016	12,005
Allenex [Member]
Indefinite Lived Intangible Assets By Major Class [Line Items]
Balance as of December 31, 2015	0
Goodwill acquired	16,786
Foreign currency translation adjustments	(719)
Balance as of June 30, 2016	$ 16,067