Employee Benefits - Costs by Plans (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 39	$ 48
Amortization of prior service cost (credit)	28	28
Expected return on plan assets	(134)	(208)
Interest cost	103	157
Remeasurement gain, net	0	(73)
Other components	(3)	(96)
Total	36	(48)
Pension | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	34	41
Pension | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	7
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	13
Amortization of prior service cost (credit)	(32)	(32)
Expected return on plan assets	(7)	(7)
Interest cost	136	135
Remeasurement gain, net	0	0
Other components	97	96
Total	106	109
Health Care and Life | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	11
Health Care and Life | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2