Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,210)	$ (3,073)	$ (9,630)	$ (9,217)
Interest cost on projected benefit obligation	835	1,252	2,506	3,757
Net amortization and deferral	1,529	1,330	4,587	3,989
Net periodic expense (benefit)	$ (846)	$ (491)	$ (2,537)	$ (1,471)