Postretirement Benefit Plans - Defined Contribution Plan Expenses for Company's Qualified Contribution Plans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	$ 2,973	$ 2,755
Retirement Savings Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	2,125	2,048
Profit Sharing Contributions [Member]
Defined Contribution Plan Disclosure [Line Items]
Total defined contribution plan expenses	$ 848	$ 707