Nature of the Business - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
PCR testing, amount recorded, COVID-19		$ 6,100		$ 6,061	$ 0
PCR testing, write-offs, COVID-19		5,300
PCR testing, general and administrative expenses, COVID-19	$ 0	$ 800
COVID-19, grant income			$ 0		7,900
COVID-19, deferred social security payroll tax	5,900			5,900		$ 5,900
COVID-19, Employee Retention Tax Credit	$ 3,700		$ 1,100	$ 4,400	$ 1,100