Pension and Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Defined benefit plan contributions	$ 0.0	$ 0.1
Unfunded liability plans	$ 9.5		$ 9.7