Revenue Recognition (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended				9 Months Ended		12 Months Ended
	Jul. 31, 2021	Feb. 28, 2019	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Sep. 30, 2019	Aug. 31, 2019
Refunds of revenues previously deferred							$ 10,000
Deferred revenue, Long-term			$ 22,706				22,706				$ 22,805
Other assets			13,202				13,202				14,743
Deferred revenue			32,373				32,373				72,930
Deferred revenue, current portion			9,667				9,667				50,125
Total revenues			158,116		$ 98,143		452,458	$ 278,627
Deferred revenue, long-term portion			22,706				22,706				$ 22,805
Revenue recognized during the period that was included in deferred revenues at the beginning of the period							32,864
Product
Revenue recognized			1,600		1,100		4,600	2,700
Cost of revenues			76,838		46,873		211,387	131,124
Total revenues			150,651		93,286		$ 406,265	260,746
Product | Minimum
Billing collection period (in months)							9 months
Product | Maximum
Billing collection period (in months)							12 months
Licensing and other
Cost of revenues			4,533		4,948		$ 12,909	12,614
Total revenues			7,465		$ 4,857		46,193	$ 17,881
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
Revenue recognized during the period that was included in deferred revenues at the beginning of the period							$ 28,600
Qiagen | Volume, regulatory and commercial milestones
Revenue, remaining performance obligation										$ 10,000
Qiagen | Other licensing and other revenue
Refunds of revenues previously deferred				$ 10,000
Deferred revenue				$ 28,600
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 Genomics
Proceeds from license agreement		$ 50,000				$ 35,600
Receivable						$ 2,500
Agreement term		10 years
Deferred revenue, current portion			3,500				$ 3,500
BGI Genomics | Sequencing services
Other assets												$ 6,000
BGI Genomics | Sequencing products
Other assets												4,000
BGI Genomics | Sequencing products and services
Other assets												$ 10,000
Foundation Medicine ("FMI")
Proceeds from license agreement									$ 16,300
Deferred revenue, current portion			3,700				3,700
Foundation Medicine ("FMI") | Milestone payments
Proceeds from license agreement	$ 1,000
Deferred revenue, current portion			$ 1,000				1,000
Foundation Medicine ("FMI") | Upfront licensing fees and prepaid revenues
Initial transaction price													$ 13,300
Foundation Medicine ("FMI") | Developmental, regulatory, and commercial milestones
Initial transaction price													$ 32,000
Foundation Medicine ("FMI") | Developmental performance milestones
Proceeds from license agreement									3,000
Foundation Medicine ("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							$ 4,000