Severance and Other Separation Costs - Schedule of Restructuring Program Activity (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restructuring Cost And Reserve [Line Items]
Severance and other separation costs	$ 1,600
2020 Restructuring Program [Member]
Restructuring Cost And Reserve [Line Items]
Liability, beginning balance	145
Severance and other separation costs		$ 2,658
Payments made	$ (145)	(2,513)
Liability, ending balance		$ 145