Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Cost for Defined Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Settlement gain	$ (12)	$ 0	$ 0
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	10	11	18
Interest cost on benefit obligation	114	115	82
Expected return on plan assets	(200)	(201)	(188)
Amortization of prior service cost	0	0	1
Amortization of net actuarial (gain) loss	(2)	(2)	20
Settlement gain	(12)
Net periodic pension benefit	$ (90)	$ (77)	$ (67)
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
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other costs of operations	Other costs of operations	Other costs of operations
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2	$ 3
Interest cost on benefit obligation	3	3	2
Amortization of prior service cost	(2)	(2)	(3)
Amortization of net actuarial (gain) loss	(3)	(3)	(1)
Net periodic pension benefit	$ (1)	$ 0	$ 1
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
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other costs of operations	Other costs of operations	Other costs of operations