Benefit Plans - Defined Benefit Pension Plan (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Service cost – benefits earned during year	$ 616	$ 568
Interest cost on projected benefit obligation	842	1,121
Expected return on plan assets	(2,763)	(2,594)
Amortization of prior service cost	(8)	(9)
Amortization of net loss	675	793
Net periodic pension income	$ (638)	$ (121)