Revenue Recognition - Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 77,909	$ 65,280	$ 219,088	$ 190,689
Previously delivered tests, revenue recognized			(18,943)
United States
Disaggregation of Revenue [Line Items]
Total revenues	64,839	58,651	187,515	165,646
Americas, excluding U.S.
Disaggregation of Revenue [Line Items]
Total revenues	806	932	2,391	2,629
Europe, Middle East, India, Africa
Disaggregation of Revenue [Line Items]
Total revenues	3,497	3,711	11,819	16,789
Other
Disaggregation of Revenue [Line Items]
Total revenues	8,767	1,986	17,363	5,625
Insurance carriers
Disaggregation of Revenue [Line Items]
Total revenues	51,801	50,631	152,779	143,094
Laboratory partners
Disaggregation of Revenue [Line Items]
Total revenues	16,938	9,162	42,093	34,182
Patients
Disaggregation of Revenue [Line Items]
Total revenues	9,170	5,487	24,216	13,413
Panorama NIPT
Disaggregation of Revenue [Line Items]
Total revenues	37,556	35,999	111,269	104,981
HCS
Disaggregation of Revenue [Line Items]
Total revenues	26,149	23,565	73,184	63,248
Other genetic tests
Disaggregation of Revenue [Line Items]
Total revenues	3,231	3,098	10,946	9,055
Product
Disaggregation of Revenue [Line Items]
Total revenues	66,936	62,662	195,399	177,284
Constellation
Disaggregation of Revenue [Line Items]
Total revenues	1,251	1,054	3,895	3,652
Qiagen
Disaggregation of Revenue [Line Items]
Total revenues			675
BGI
Disaggregation of Revenue [Line Items]
Total revenues	6,844		11,862
Other, licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	2,878	1,564	7,257	9,753
Licensing and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 10,973	$ 2,618	$ 23,689	$ 13,405