Defined Benefit Plans - Net Periodic Cost (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Retirement Benefits [Abstract]
Expected return on plan assets, net of expenses	$ (3,210)	$ (3,072)	$ (6,420)	$ (6,144)
Interest cost on projected benefit obligation	836	1,253	1,671	2,505
Net amortization and deferral	1,529	1,329	3,058	2,659
Net periodic expense (benefit)	$ (845)	$ (490)	$ (1,691)	$ (980)