Revenue Recognition (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 31, 2019	Feb. 28, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Revenue recognized					$ 1,622	$ 1,263
Cost of revenues			$ 42,731	$ 41,382	84,251	82,987
Deferred revenue, Long-term			22,533		22,533		$ 23,808
Other assets			12,357		12,357		12,476
Deferred revenue			74,925		74,925		79,824
Deferred revenue, current portion			52,392		52,392		56,016
Total revenues			86,472	74,355	180,484	141,179
Deferred revenue, long-term portion			22,533		22,533		23,808
Revenue recognized during the period that was included in deferred revenues at the beginning of the period					4,943
Product
Revenue recognized			600	800	1,600	1,300
Total revenues			80,414	65,099	$ 167,460	128,463
Product | Minimum
Billing collection period (in months)					9 months
Product | Maximum
Billing collection period (in months)					12 months
Licensing and other
Cost of revenues			4,208	2,443	$ 7,666	4,141
Total revenues			6,058	9,256	13,024	12,716
Genetic testing services
Revenue recognized during the period that was included in deferred revenues at the beginning of the period					$ 300
Qiagen
Proceeds from license agreement								$ 5,000
Agreement term					10 years
Revenue, remaining performance obligation								40,000
Qiagen | Volume, regulatory and commercial milestones
Revenue, remaining performance obligation								$ 10,000
Qiagen | Prepaid royalty
Revenue recognized			0
Laboratory distribution partners | Product | Minimum
Billing collection period (in months)					2 months
Laboratory distribution partners | Product | Maximum
Billing collection period (in months)					3 months
BGI
Proceeds from license agreement		$ 50,000		35,600
Receivable				$ 2,500		$ 2,500
Agreement term		10 years
Deferred revenue, current portion			500		$ 500
BGI | Sequencing services
Other assets									$ 6,000
BGI | Sequencing products
Other assets									4,000
BGI | Sequencing products and services
Other assets			$ 10,000		10,000				$ 10,000
Foundation Medicine, Inc. ("FMI")
Proceeds from license agreement					0		16,300
Agreement term	5 years
Automatic renewals, successive period thereafter	1 year
Foundation Medicine, Inc. ("FMI") | Upfront licensing fees and prepaid revenues
Initial transaction price	$ 13,300
Foundation Medicine, Inc. ("FMI") | Developmental, regulatory, and commercial milestones
Initial transaction price	$ 32,000
Foundation Medicine, Inc. ("FMI") | Developmental performance milestones
Proceeds from license agreement							3,000
Foundation Medicine, Inc. ("FMI") | Licensing fees and prepaid revenue
Proceeds from license agreement							$ 13,300
BGI and FMI | Genetic testing services
Revenue recognized during the period that was included in deferred revenues at the beginning of the period					$ 4,600