Revenue Recognition - Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 66,824	$ 62,340
Previously delivered tests, revenue recognized	(1,493)
Decrease to loss from operations	(31,746)	(30,517)
United States
Disaggregation of Revenue [Line Items]
Total revenues	60,283	50,364
Americas, excluding U.S.
Disaggregation of Revenue [Line Items]
Total revenues	818	850
Europe, Middle East, India, Africa
Disaggregation of Revenue [Line Items]
Total revenues	4,004	9,322
Other
Disaggregation of Revenue [Line Items]
Total revenues	1,719	1,804
Insurance carriers
Disaggregation of Revenue [Line Items]
Total revenues	50,201	44,142
Laboratory partners
Disaggregation of Revenue [Line Items]
Total revenues	10,023	14,888
Patients
Disaggregation of Revenue [Line Items]
Total revenues	6,600	3,310
Panorama NIPT
Disaggregation of Revenue [Line Items]
Total revenues	37,246	33,267
HCS
Disaggregation of Revenue [Line Items]
Total revenues	22,749	18,262
Other genetic tests
Disaggregation of Revenue [Line Items]
Total revenues	3,369	2,740
Product
Disaggregation of Revenue [Line Items]
Total revenues	63,364	54,269
Constellation
Disaggregation of Revenue [Line Items]
Total revenues	1,332	1,305
Qiagen
Disaggregation of Revenue [Line Items]
Total revenues	148	5,500
Other, licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	1,980	1,266
Licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 3,460	$ 8,071