Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 61,896	$ 56,885	$ 59,040	$ 55,771
Changes in unrealized gains (losses), Investment Securities Available-For-Sale	975	1,297	1,681	1,048
Changes in unrealized gains (losses), Derivative Hedges	(5)	460	436	8
Changes in unrealized gains (losses), Debit Valuation Adjustments	(5)	0	(8)	0
Changes in unrealized gains (losses)	965	1,757	2,109	1,056
Foreign currency translation adjustment	(1)	12	(5)	16
Reclassification to earnings of realized (gains) losses	195	328	609	736
Applicable income taxes	(298)	(535)	(697)	(458)
Ending Balance	63,798	59,321	63,798	59,321
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(8,609)	(10,308)	(9,764)	(10,096)
Ending Balance	(7,748)	(8,746)	(7,748)	(8,746)
Unrealized Gains (Losses) on Investment Securities Available-For-Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(4,513)	(5,310)	(5,078)	(5,151)
Changes in unrealized gains (losses), Investment Securities Available-For-Sale	975	1,297	1,681	1,048
Reclassification to earnings of realized (gains) losses	7	119	64	153
Applicable income taxes	(248)	(361)	(446)	(305)
Ending Balance	(3,779)	(4,255)	(3,779)	(4,255)
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	(2,992)	(3,354)	(3,165)	(3,537)
Reclassification to earnings of realized (gains) losses	124	132	358	377
Applicable income taxes	(32)	(33)	(93)	(95)
Ending Balance	(2,900)	(3,255)	(2,900)	(3,255)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(132)	(482)	(553)	(242)
Changes in unrealized gains (losses), Derivative Hedges	(5)	460	436	8
Reclassification to earnings of realized (gains) losses	65	77	191	206
Applicable income taxes	(15)	(138)	(161)	(55)
Ending Balance	(87)	(83)	(87)	(83)
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(954)	(1,138)	(955)	(1,138)
Reclassification to earnings of realized (gains) losses	(1)		(4)
Applicable income taxes	(4)
Ending Balance	(959)	(1,138)	(959)	(1,138)
Debit Valuation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1)	0	1	0
Changes in unrealized gains (losses), Derivative Hedges			(8)
Changes in unrealized gains (losses), Debit Valuation Adjustments	(5)
Applicable income taxes	1		2
Ending Balance	(5)	0	(5)	0
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(17)	(24)	(14)	(28)
Foreign currency translation adjustment	(1)	12	(5)	16
Applicable income taxes	0	(3)	1	(3)
Ending Balance	$ (18)	$ (15)	$ (18)	$ (15)