Postretirement Benefit Plans - Defined Contribution Plan Expenses for Company's Qualified Contribution Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	$ 3,756	$ 3,431	$ 11,326	$ 11,179
Retirement Savings Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	1,897	2,055	6,042	6,072
Profit Sharing Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	$ 1,859	$ 1,376	$ 5,284	$ 5,107