Pension Plans and Other Postretirement Benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	$ (206,274)	$ 238,218
Amortization of prior service (cost) credit	4,185	4,181	$ 4,173
Amortization of actuarial (loss) gain	(87,722)	(56,860)	$ (20,745)
Total recognized in other comprehensive income, pre-tax	(289,811)	185,539
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	(204,042)	235,847
Amortization of prior service (cost) credit	(553)	(557)
Amortization of actuarial (loss) gain	(89,017)	(58,096)
Total recognized in other comprehensive income, pre-tax	(293,612)	177,194
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net loss (gain)	(2,232)	2,371
Amortization of prior service (cost) credit	4,738	4,738
Amortization of actuarial (loss) gain	1,295	1,236
Total recognized in other comprehensive income, pre-tax	$ 3,801	$ 8,345