Revenue Recognition - Disaggregation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 94,012	$ 66,824
Decrease to loss from operations	$ (34,872)	$ (31,746)
Basic and diluted (in dollars per share)	$ (0.45)	$ (0.54)
United States
Disaggregation of Revenue [Line Items]
Total revenues	$ 86,731	$ 60,283
Americas, excluding U.S.
Disaggregation of Revenue [Line Items]
Total revenues	782	818
Europe, Middle East, India, Africa
Disaggregation of Revenue [Line Items]
Total revenues	3,476	4,004
Asia Pacific and Other
Disaggregation of Revenue [Line Items]
Total revenues	3,023	1,719
Insurance carriers
Disaggregation of Revenue [Line Items]
Total revenues	70,672	50,201
Laboratory and other partners
Disaggregation of Revenue [Line Items]
Total revenues	15,683	10,023
Patients
Disaggregation of Revenue [Line Items]
Total revenues	7,657	6,600
Product
Disaggregation of Revenue [Line Items]
Total revenues	87,046	63,364
Upfront license and constellation and paternity
Disaggregation of Revenue [Line Items]
Total revenues	1,367	1,332
License and development services
Disaggregation of Revenue [Line Items]
Total revenues	4,802	148
Other, licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	797	1,980
Licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 6,966	$ 3,460