Pension Plans and Other Postretirement Benefits - Net Periodic Defined Benefit Cost for Defined Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4,543	$ 5,234	$ 8,814	$ 10,257
Interest cost on projected benefit obligation	22,080	15,502	38,347	30,936
Expected return on plan assets	(50,083)	(35,774)	(87,233)	(71,724)
Amortization of prior service cost (credit)	133	151	258	276
Amortization of net actuarial loss (gain)	5,322	22,359	9,947	44,509
Net periodic cost (benefit)	(18,005)	7,472	(29,867)	14,254
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	993	258	1,225	506
Interest cost on projected benefit obligation	671	329	1,026	656
Amortization of prior service cost (credit)	(311)	(1,194)	(1,386)	(2,369)
Amortization of net actuarial loss (gain)	(416)	(347)	(741)	(647)
Net periodic cost (benefit)	$ 937	$ (954)	$ 124	$ (1,854)