Revenue Recognition (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			12 Months Ended
	Aug. 31, 2019	Feb. 28, 2019	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2019
Revenue recognized			$ 1,027		$ 478
Cost of revenues			41,520		41,605
Deferred revenue, Long-term			25,152				$ 23,808
Other assets			12,093				12,476
Deferred revenue			76,992				79,824
Deferred revenue, current portion			51,840				56,016
Total revenues			94,012		66,824
Deferred revenue, long-term portion			25,152				$ 23,808
Revenue recognized during the period that was included in deferred revenues at the beginning of the period			(3,455)
Product
Revenue recognized			1,000		500
Total revenues			$ 87,046		63,364
Product | Minimum
Billing collection period (in months)			9 months
Product | Maximum
Billing collection period (in months)			12 months
Licensing and other
Cost of revenues			$ 3,458		1,698
Total revenues			6,966		$ 3,460
Genetic testing services
Revenue recognized during the period that was included in deferred revenues at the beginning of the period			$ (200)
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
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
Agreement term		10 years
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
Foundation Medicine, Inc. ("FMI")
Proceeds from license agreement			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			$ (3,300)