Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension settlement charge	$ 1,665	$ 0	$ 0
Qualified Defined  Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	106	101	516
Interest cost	1,220	1,538	1,806
Expected return on plan assets	(2,146)	(2,264)	(2,300)
Recognized net actuarial losses (gains)	902	849	1,404
Amortization of net prior service (credits) costs	(349)	(342)	(333)
Pension settlement charge	1,665	0	0
Non-service FAS pension expense (income)	1,292	(219)	577
Net periodic benefit expense (income)	1,398	(118)	1,093
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	13	14
Interest cost	53	70	97
Expected return on plan assets	(141)	(127)	(110)
Recognized net actuarial losses (gains)	0	(4)	2
Amortization of net prior service (credits) costs	37	39	42
Pension settlement charge	0	0	0
Non-service FAS pension expense (income)	(51)	(22)	31
Net periodic benefit expense (income)	$ (38)	$ (9)	$ 45