Postretirement Benefits - Activity for the SERP (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Premiums paid for insurance coverage	$ 2,193	$ 2,480	$ 2,394
Total investments:
Company owned life insurance	52,791	51,361
Exchange traded funds	87,133	75,390
Total investments of SERP	$ 139,924	$ 126,751