Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,210)	$ (3,072)
Interest cost on projected benefit obligation	835	1,252
Net amortization and deferral	1,529	1,330
Net periodic expense (benefit)	$ (846)	$ (490)