Employee Benefits - Costs by Plans (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 52	$ 66	$ 105	$ 132
Amortization of prior service cost (credit)	28	15	56	30
Expected return on plan assets	(253)	(294)	(506)	(591)
Interest cost	188	114	376	224
Remeasurement loss, net	0	198	0	198
Other components	(37)	33	(74)	(139)
Total	15	99	31	(7)
Pension | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	45	58	91	116
Pension | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	8	14	16
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	24	27	47
Amortization of prior service cost (credit)	(104)	(110)	(209)	(313)
Expected return on plan assets	(8)	(7)	(15)	(14)
Interest cost	136	83	272	166
Remeasurement loss, net	0	0	0	0
Other components	24	(34)	48	(161)
Total	38	(10)	75	(114)
Health Care and Life | Cost of services
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	20	23	40
Health Care and Life | Selling, general and administrative expense
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 4	$ 4	$ 7