Employee Benefits - Costs by Plans (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 41	$ 45		$ 80	$ 93
Amortization of prior service cost (credit)	28	28		56	56
Expected return on plan assets	(134)	(140)		(268)	(348)
Interest cost	101	112		204	269
Remeasurement loss, net	45	136	$ (73)	45	63
Other components	40	136		37	40
Total	81	181		117	133
Pension | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	35	39		69	80
Pension | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	6		11	13
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	13		17	26
Amortization of prior service cost (credit)	(32)	(32)		(64)	(64)
Expected return on plan assets	(7)	(7)		(14)	(14)
Interest cost	137	136		273	271
Remeasurement loss, net	0	0		0	0
Other components	98	97		195	193
Total	106	110		212	219
Health Care and Life | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	11		14	22
Health Care and Life | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2		$ 3	$ 4