Stockholders' Equity - Changes in Balance of Accumulated Other Comprehensive Loss, Net of Income Taxes (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 9,266	$ 10,959	$ 6,038
Other comprehensive income (loss) before reclassifications	(666)	1,714	3,319
Amounts reclassified from AOCL
Amounts reclassified from AOCL	(114)	1,269	1,796
Other comprehensive income, net of tax	(780)	2,983	5,115
Ending balance	6,835	9,266	10,959
Non-cash, non-operating pension settlement charge		1,500	1,700
Non-cash, non-operating pension settlement charge, after tax		$ 1,200	$ 1,300
Non-cash, non-operating pension settlement charge, per share, after tax (in dollars per share)		$ 4.33	$ 4.72
Postretirement Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(7,866)	$ (10,964)	$ (16,155)
Other comprehensive income (loss) before reclassifications	(689)	1,873	3,404
Amounts reclassified from AOCL
Amounts reclassified from AOCL	(149)	1,225	1,787
Other comprehensive income, net of tax	(838)	3,098	5,191
Ending balance	(8,704)	(7,866)	(10,964)
AOCI related to postretirement benefit plans, tax benefit	2,300	2,100	3,000
Other, net
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(157)	(42)	34
Other comprehensive income (loss) before reclassifications	23	(159)	(85)
Amounts reclassified from AOCL
Amounts reclassified from AOCL	35	44	9
Other comprehensive income, net of tax	58	(115)	(76)
Ending balance	(99)	(157)	(42)
AOCL
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(8,023)	(11,006)	(16,121)
Amounts reclassified from AOCL
Other comprehensive income, net of tax	(780)	2,983	5,115
Ending balance	(8,803)	(8,023)	(11,006)
Recognition of settlement loss
Amounts reclassified from AOCL
Amounts reclassified from AOCL		1,156	1,310
Recognition of net actuarial losses
Amounts reclassified from AOCL
Amounts reclassified from AOCL	116	337	733
Amortization of net prior service credits
Amounts reclassified from AOCL
Amounts reclassified from AOCL	(265)	(268)	(256)
Other
Amounts reclassified from AOCL
Amounts reclassified from AOCL	$ 35	$ 44	$ 9