Pension Plans and Other Postretirement Benefits - Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net gain	$ (125)	$ (84)
Net prior service cost		13
Amortization of prior service (cost) credit	2	2	$ 4
Amortization of actuarial (loss) gain	5	(18)	$ (88)
Total recognized in other comprehensive income, pre-tax	(118)	(87)
Pension Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net gain	(120)	(62)
Amortization of prior service (cost) credit		(1)
Amortization of actuarial (loss) gain	2	(20)
Total recognized in other comprehensive income, pre-tax	118	(83)
Other Postretirement Benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Net gain	(5)	(22)
Net prior service cost		13
Amortization of prior service (cost) credit	2	3
Amortization of actuarial (loss) gain	$ 3	2
Total recognized in other comprehensive income, pre-tax		$ (4)