Employee Benefits - Benefit (Income) Cost Related to Pension and Postretirement Health Care and Life Insurance Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Remeasurement loss (gain), net	$ (657)	$ 992	$ (1,700)
Other components	(300)	938	(2,386)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	185	208	246
Amortization of prior service cost (credit)	112	112	82
Expected return on plan assets	(620)	(1,013)	(1,119)
Interest cost	479	752	544
Remeasurement loss (gain), net	(110)	266	1,505
Curtailment and termination benefits	0	0	2
Other components	(139)	117	1,014
Total	46	325	1,260
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	52	54	94
Amortization of prior service cost (credit)	(129)	(419)	(530)
Expected return on plan assets	(28)	(31)	(27)
Interest cost	543	545	332
Remeasurement loss (gain), net	(547)	726	(3,182)
Curtailment and termination benefits	0	0	0
Other components	(161)	821	(3,407)
Total	(109)	875	(3,313)
Cost of services | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	159	182	216
Cost of services | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	46	79
Selling, general and administrative expense | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	26	26	30
Selling, general and administrative expense | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8	$ 8	$ 15