Pension Plans and Other Postretirement Benefits - Net Periodic Defined Benefit Cost for Defined Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4,271	$ 5,023
Interest cost on projected benefit obligation	16,267	15,434
Expected return on plan assets	(37,150)	(35,950)
Amortization of prior service cost (credit)	125	125
Amortization of net actuarial loss (gain)	4,625	22,150
Net periodic cost (benefit)	(11,862)	6,782
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	232	248
Interest cost on projected benefit obligation	355	327
Amortization of prior service cost (credit)	(1,075)	(1,175)
Amortization of net actuarial loss (gain)	(325)	(300)
Net periodic cost (benefit)	$ (813)	$ (900)