Postretirement Benefits - Activity for the SERP (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Retirement Benefits [Abstract]
Premiums paid for insurance coverage	$ 443	$ 443
Total investments:
Company owned life insurance	53,982		$ 52,791
Exchange traded funds	72,401		87,133
Total investments of SERP	$ 126,383		$ 139,924