Postretirement Benefits - Components of Net Periodic Pension Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Retirement Benefits [Abstract]
Service cost	$ 8,656	$ 7,918	$ 17,311	$ 15,836
Interest cost	6,121	5,469	12,244	10,936
Expected return on assets	(8,885)	(8,083)	(17,770)	(16,166)
Prior service cost	158	158	316	316
Actuarial (gain) loss	3,208	4,984	6,417	9,969
Net periodic benefit cost	$ 9,258	$ 10,446	$ 18,518	$ 20,891