Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 56,033	$ 53,454	$ 55,771	$ 51,232
Changes in unrealized gains (losses)	(78)	(460)	(249)	845
Changes in unrealized gains (losses)	(109)	(465)	(452)	(261)
Changes in unrealized gains (losses)	0	0	0	1
Changes in unrealized gains (losses)	(187)	(925)	(701)	585
Foreign currency translation adjustment	(2)	19	4	18
Reclassification to earnings of realized (gains) losses	247	147	408	305
Applicable income taxes	(13)	194	77	(219)
Ending Balance	56,885	53,484	56,885	53,484
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(10,353)	(10,153)	(10,096)	(11,407)
Ending Balance	(10,308)	(10,718)	(10,308)	(10,718)
Unrealized Gains (Losses) on Investment Securities Available-for- Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(5,279)	(5,369)	(5,151)	(6,378)
Changes in unrealized gains (losses)	(78)	(460)	(249)	845
Reclassification to earnings of realized (gains) losses	36	(3)	34	29
Applicable income taxes	11	116	56	(212)
Ending Balance	(5,310)	(5,716)	(5,310)	(5,716)
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	(3,452)	(3,843)	(3,537)	(3,933)
Reclassification to earnings of realized (gains) losses	131	141	245	262
Applicable income taxes	(33)	(35)	(62)	(66)
Ending Balance	(3,354)	(3,737)	(3,354)	(3,737)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(461)	43	(242)	(114)
Changes in unrealized gains (losses)	(109)	(465)	(452)	(261)
Reclassification to earnings of realized (gains) losses	80	11	129	18
Applicable income taxes	8	117	83	63
Ending Balance	(482)	(294)	(482)	(294)
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1,138)	(940)	(1,138)	(939)
Changes in unrealized gains (losses)				1
Reclassification to earnings of realized (gains) losses		(2)		(4)
Applicable income taxes		1		1
Ending Balance	(1,138)	(941)	(1,138)	(941)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(23)	(44)	(28)	(43)
Foreign currency translation adjustment	(2)	19	4	18
Applicable income taxes	1	(5)		(5)
Ending Balance	$ (24)	$ (30)	$ (24)	$ (30)