Benefit Plans - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 616,000	$ 568,000
Periodic pension income	1,300,000	$ 700,000
Minimum required pension plan contribution	5,200,000
Available credit balance	64,200,000
Expected voluntary contribution for the year 2021	$ 0