Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 55,771	$ 51,232
Changes in unrealized gains (losses)	(171)	1,305
Changes in unrealized gains (losses)	(343)	204
Changes in unrealized gains (losses)	0	1
Changes in unrealized gains (losses)	(514)	1,510
Foreign currency translation adjustment	6	(1)
Reclassification to earnings of realized (gains) losses	161	158
Applicable income taxes	90	(413)
Ending Balance	56,033	53,454
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(10,096)	(11,407)
Ending Balance	(10,353)	(10,153)
Unrealized Gains (Losses) on Investment Securities Available-for- Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(5,151)	(6,378)
Changes in unrealized gains (losses)	(171)	1,305
Reclassification to earnings of realized (gains) losses	(2)	32
Applicable income taxes	45	(328)
Ending Balance	(5,279)	(5,369)
Unrealized Gains (Losses) on Investment Securities Transferred From Available- for-Sale to Held-to-Maturity
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(3,537)	(3,933)
Reclassification to earnings of realized (gains) losses	114	121
Applicable income taxes	(29)	(31)
Ending Balance	(3,452)	(3,843)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(242)	(114)
Changes in unrealized gains (losses)	(343)	204
Reclassification to earnings of realized (gains) losses	49	7
Applicable income taxes	75	(54)
Ending Balance	(461)	43
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1,138)	(939)
Changes in unrealized gains (losses)	0	1
Reclassification to earnings of realized (gains) losses	0	(2)
Applicable income taxes	0	0
Ending Balance	(1,138)	(940)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(28)	(43)
Foreign currency translation adjustment	6	(1)
Applicable income taxes	(1)	0
Ending Balance	$ (23)	$ (44)