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, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Other components	$ (3,785)	$ 425	$ (627)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	282	305	247
Amortization of prior service cost (credit)	61	61	61
Expected return on plan assets	(1,234)	(1,186)	(1,130)
Interest cost	394	505	695
Remeasurement loss (gain), net	(1,419)	744	606
Other components	(2,198)	124	232
Total	(1,916)	429	479
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	112	110	96
Amortization of prior service cost (credit)	(894)	(966)	(971)
Expected return on plan assets	(22)	(28)	(37)
Interest cost	289	429	629
Remeasurement loss (gain), net	(960)	866	(480)
Other components	(1,587)	301	(859)
Total	(1,475)	411	(763)
Cost of services | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	247	245	202
Cost of services | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	94	89	78
Selling, general and administrative expense | Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	35	60	45
Selling, general and administrative expense | Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 18	$ 21	$ 18