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, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Net gain	$ (305)	$ (125)
Amortization of prior service credit	2	2
Amortization of actuarial gain	5	5
Settlement gain	12
Total recognized in other comprehensive income, pre-tax	(286)	(118)
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net gain	(298)	(120)
Amortization of prior service credit	0	0
Amortization of actuarial gain	2	2
Settlement gain	12
Total recognized in other comprehensive income, pre-tax	(284)	(118)
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Net gain	(7)	(5)
Amortization of prior service credit	2	2
Amortization of actuarial gain	3	3
Settlement gain	0
Total recognized in other comprehensive income, pre-tax	$ (2)	$ 0