Revenue Recognition - Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 74,355	$ 63,069	$ 141,179	$ 125,409
Previously delivered tests, revenue recognized			(9,299)
Decrease to loss from operations	(28,636)	(27,218)	(60,382)	(57,735)
United States
Disaggregation of Revenue [Line Items]
Total revenues	62,393	56,631	122,676	106,995
Americas, excluding U.S.
Disaggregation of Revenue [Line Items]
Total revenues	767	847	1,585	1,697
Europe, Middle East, India, Africa
Disaggregation of Revenue [Line Items]
Total revenues	4,318	3,756	8,322	13,078
Other
Disaggregation of Revenue [Line Items]
Total revenues	6,877	1,835	8,596	3,639
Insurance carriers
Disaggregation of Revenue [Line Items]
Total revenues	50,777	48,321	100,978	92,463
Laboratory partners
Disaggregation of Revenue [Line Items]
Total revenues	15,132	10,132	25,155	25,020
Patients
Disaggregation of Revenue [Line Items]
Total revenues	8,446	4,616	15,046	7,926
Panorama NIPT
Disaggregation of Revenue [Line Items]
Total revenues	36,467	35,715	73,713	68,982
HCS
Disaggregation of Revenue [Line Items]
Total revenues	24,286	21,421	47,035	39,683
Other genetic tests
Disaggregation of Revenue [Line Items]
Total revenues	4,346	3,217	7,715	5,957
Product
Disaggregation of Revenue [Line Items]
Total revenues	65,099	60,353	128,463	114,622
Constellation
Disaggregation of Revenue [Line Items]
Total revenues	1,312	1,293	2,644	2,598
Qiagen
Disaggregation of Revenue [Line Items]
Total revenues	527	94	675	5,594
BGI
Disaggregation of Revenue [Line Items]
Total revenues	5,018		5,018
Other, licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	2,399	1,329	4,379	2,595
Licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 9,256	$ 2,716	$ 12,716	$ 10,787