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, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Remeasurement loss (gain), net	$ 992	$ (1,700)	$ (2,400)
Other components	938	(2,386)	(3,785)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	208	246	282
Amortization of prior service cost (credit)	112	82	61
Expected return on plan assets	(1,013)	(1,119)	(1,234)
Interest cost	752	544	394
Remeasurement loss (gain), net	266	1,505	(1,419)
Curtailment and termination benefits	0	2	0
Other components	117	1,014	(2,198)
Total	325	1,260	(1,916)
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	54	94	112
Amortization of prior service cost (credit)	(419)	(530)	(894)
Expected return on plan assets	(31)	(27)	(22)
Interest cost	545	332	289
Remeasurement loss (gain), net	726	(3,182)	(960)
Curtailment and termination benefits	0	0	0
Other components	821	(3,407)	(1,587)
Total	875	(3,313)	(1,475)
Cost of services | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	182	216	247
Cost of services | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	46	79	94
Selling, general and administrative expense | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	26	30	35
Selling, general and administrative expense | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8	$ 15	$ 18