Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Facility rent expense	$ 3,700,000	$ 3,900,000	$ 3,500,000
Health plan annual stop-loss insurance per claim	200,000
Workers compensation insurance with no stop-loss for prior claim years	350,000
Accruals for health and workers' compensation plans	$ 2,200,000	$ 2,800,000