Stockholders' Equity - Changes in Balance of Accumulated Other Comprehensive Loss, Net of Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 6,038	$ 3,171	$ 1,449
Other comprehensive (loss) income before reclassifications	3,319	(1,011)	(2,164)
Amounts reclassified from AOCL
Amounts reclassified from AOCL	1,796	444	931
Other comprehensive income (loss), net of tax	5,115	(567)	(1,233)
Ending balance	10,959	6,038	3,171
Non-cash, non-operating pension settlement charge	1,700
Non-cash, non-operating pension settlement charge, after-tax	1,300
Postretirement Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(16,155)	(15,528)	(14,254)
Other comprehensive (loss) income before reclassifications	3,404	(1,067)	(2,182)
Amounts reclassified from AOCL
Amounts reclassified from AOCL	1,787	440	908
Other comprehensive income (loss), net of tax	5,191	(627)	(1,274)
Ending balance	(10,964)	(16,155)	(15,528)
AOCI related to postretirement benefit plans, tax benefit	3,000	4,400	4,200
Other, net
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	34	(26)	(67)
Other comprehensive (loss) income before reclassifications	(85)	56	18
Amounts reclassified from AOCL
Amounts reclassified from AOCL	9	4	23
Other comprehensive income (loss), net of tax	(76)	60	41
Ending balance	(42)	34	(26)
AOCL
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(16,121)	(15,554)	(14,321)
Amounts reclassified from AOCL
Other comprehensive income (loss), net of tax	5,115	(567)	(1,233)
Ending balance	(11,006)	(16,121)	(15,554)
Recognition of net actuarial losses
Amounts reclassified from AOCL
Amounts reclassified from AOCL	733	689	1,148
Amortization of net prior service credits
Amounts reclassified from AOCL
Amounts reclassified from AOCL	(256)	(249)	(240)
Other
Amounts reclassified from AOCL
Amounts reclassified from AOCL	9	$ 4	$ 23
Recognition of settlement loss
Amounts reclassified from AOCL
Amounts reclassified from AOCL	$ 1,310