Pension Plans and Other Postretirement Benefits - Data Relating to Funding Position of Defined Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in plan assets:
Fair value of plan assets at beginning of year	$ 3,141
Fair value of plan assets at end of year	3,203	$ 3,141
Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	2,369	2,379
Service cost	10	11	$ 18
Interest cost	$ 114	$ 115	$ 82
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other costs of operations	Other costs of operations	Other costs of operations
Plan participants’ contributions	$ 0	$ 0
Actuarial (gain) loss	(132)	13
Settlements paid	(171)	0
Benefits paid	(148)	(149)
Benefit obligation at end of year	2,042	2,369	$ 2,379
Change in plan assets:
Fair value of plan assets at beginning of year	3,145	2,942
Actual return on plan assets	366	334
Employer contributions	16	18
Plan participants’ contributions	0	0
Settlements paid	(171)	0
Benefits paid	(148)	(149)
Fair value of plan assets at end of year	3,208	3,145	2,942
Funded status	1,166	776
Prepaid asset recognized in the Consolidated Balance Sheet	1,298	922
Accrued liability recognized in the Consolidated Balance Sheet	(132)	(146)
Net accrued asset (liability) recognized in the Consolidated Balance Sheet	1,166	776
Net (gain) loss	(93)	191
Net prior service cost	0	0
Pre-tax adjustment to accumulated other comprehensive income	(93)	191
Taxes	23	(49)
Net adjustment to accumulated other comprehensive income	(70)	142
Other Postretirement Benefit Plans
Change in benefit obligation:
Benefit obligation at beginning of year	57	60
Service cost	1	2	3
Interest cost	$ 3	$ 3	$ 2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other costs of operations	Other costs of operations	Other costs of operations
Plan participants’ contributions	$ 0	$ 1
Actuarial (gain) loss	(7)	(5)
Settlements paid	0	0
Benefits paid	(3)	(4)
Benefit obligation at end of year	51	57	$ 60
Change in plan assets:
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	2	3
Plan participants’ contributions	1	1
Settlements paid	0	0
Benefits paid	(3)	(4)
Fair value of plan assets at end of year	0	0	$ 0
Funded status	(51)	(57)
Prepaid asset recognized in the Consolidated Balance Sheet	0	0
Accrued liability recognized in the Consolidated Balance Sheet	(51)	(57)
Net accrued asset (liability) recognized in the Consolidated Balance Sheet	(51)	(57)
Net (gain) loss	(41)	(37)
Net prior service cost	3	1
Pre-tax adjustment to accumulated other comprehensive income	(38)	(36)
Taxes	10	9
Net adjustment to accumulated other comprehensive income	$ (28)	$ (27)