Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension settlement charge	$ 0	$ (1,470)	$ (1,665)
Qualified Defined  Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	(65)	(87)	(106)
Interest cost	(1,459)	(1,289)	(1,220)
Expected return on plan assets	1,722	1,854	2,146
Recognized net actuarial (losses) gains	(168)	(425)	(902)
Amortization of prior service credits (costs)	348	359	349
Pension settlement charge	0	(1,470)	(1,665)
Non-service FAS income (expense)	443	(971)	(1,292)
Total FAS income (expense)	378	(1,058)	(1,398)
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	(5)	(9)	(13)
Interest cost	(68)	(49)	(53)
Expected return on plan assets	103	136	141
Recognized net actuarial (losses) gains	31	46	0
Amortization of prior service credits (costs)	(10)	(27)	(37)
Pension settlement charge	0	0	0
Non-service FAS income (expense)	56	106	51
Total FAS income (expense)	$ 51	$ 97	$ 38