Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 60,558	$ 56,033	$ 59,040	$ 55,771
Changes in unrealized gains (losses)	198	(78)	706	(249)
Changes in unrealized gains (losses)	157	(109)	441	(452)
Changes in unrealized gains (losses), debit valuation adjustments	(5)	0	(3)	0
Changes in unrealized gains (losses)	350	(187)	1,144	(701)
Foreign currency translation adjustment	(8)	(2)	(4)	4
Reclassification to earnings of realized (gains) losses	244	247	414	408
Applicable income taxes	(153)	(13)	(399)	77
Ending Balance	61,896	56,885	61,896	56,885
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(9,042)	(10,353)	(9,764)	(10,096)
Ending Balance	(8,609)	(10,308)	(8,609)	(10,308)
Unrealized Gains (Losses) on Investment Securities Available-for- Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(4,699)	(5,279)	(5,078)	(5,151)
Changes in unrealized gains (losses)	198	(78)	706	(249)
Reclassification to earnings of realized (gains) losses	57	36	57	34
Applicable income taxes	(69)	11	(198)	56
Ending Balance	(4,513)	(5,310)	(4,513)	(5,310)
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	(3,082)	(3,452)	(3,165)	(3,537)
Reclassification to earnings of realized (gains) losses	123	131	234	245
Applicable income taxes	(33)	(33)	(61)	(62)
Ending Balance	(2,992)	(3,354)	(2,992)	(3,354)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(297)	(461)	(553)	(242)
Changes in unrealized gains (losses)	157	(109)	441	(452)
Reclassification to earnings of realized (gains) losses	66	80	126	129
Applicable income taxes	(58)	8	(146)	83
Ending Balance	(132)	(482)	(132)	(482)
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(956)	(1,138)	(955)	(1,138)
Reclassification to earnings of realized (gains) losses	(2)		(3)
Applicable income taxes	4		4
Ending Balance	(954)	(1,138)	(954)	(1,138)
Debit Valuation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	2	0	1	0
Changes in unrealized gains (losses)			(3)
Changes in unrealized gains (losses), debit valuation adjustments	(5)
Applicable income taxes	2		1
Ending Balance	(1)	0	(1)	0
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(10)	(23)	(14)	(28)
Foreign currency translation adjustment	(8)	(2)	(4)	4
Applicable income taxes	1	1	1
Ending Balance	$ (17)	$ (24)	$ (17)	$ (24)