Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue
Total product revenues	$ 95,619	$ 85,487	$ 188,244	$ 169,467
Invasive breast cancer test
Disaggregation of Revenue
Total product revenues	86,478	78,517	171,029	156,575
Prostate cancer test
Disaggregation of Revenue
Total product revenues	6,777	4,154	12,617	7,504
Other
Disaggregation of Revenue
Total product revenues	$ 2,364	$ 2,816	$ 4,598	$ 5,388