Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net loss attributable to CareDx, Inc.	$ (10,470)	$ (3,185)	$ (20,223)	$ (5,457)
Denominator:
Weighted-average shares used to compute basic and diluted net loss per share attributable to CareDx, Inc.	13,568,120	11,835,405	12,768,913	11,824,993
Net loss per share attributable to CareDx, Inc.:
Basic and diluted	$ (0.77)	$ (0.27)	$ (1.58)	$ (0.46)