Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 59,040	$ 55,771
Changes in unrealized gains (losses)	508	(171)
Changes in unrealized gains (losses)	284	(343)
Changes in unrealized gains (losses), debit valuation adjustments	2	0
Changes in unrealized gains (losses)	794	(514)
Foreign currency translation adjustment	4	6
Reclassification to earnings of realized (gains) losses	170	161
Applicable income taxes	(246)	90
Ending Balance	60,558	56,033
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(9,764)	(10,096)
Ending Balance	(9,042)	(10,353)
Unrealized Gains (Losses) on Investment Securities Available-for- Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(5,078)	(5,151)
Changes in unrealized gains (losses)	508	(171)
Reclassification to earnings of realized (gains) losses	0	(2)
Applicable income taxes	(129)	45
Ending Balance	(4,699)	(5,279)
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	(3,165)	(3,537)
Reclassification to earnings of realized (gains) losses	111	114
Applicable income taxes	(28)	(29)
Ending Balance	(3,082)	(3,452)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(553)	(242)
Changes in unrealized gains (losses)	284	(343)
Reclassification to earnings of realized (gains) losses	60	49
Applicable income taxes	(88)	75
Ending Balance	(297)	(461)
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(955)	(1,138)
Reclassification to earnings of realized (gains) losses	(1)
Ending Balance	(956)	(1,138)
Debit Valuation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	1	0
Changes in unrealized gains (losses), debit valuation adjustments	2
Applicable income taxes	(1)
Ending Balance	2	0
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(14)	(28)
Foreign currency translation adjustment	4	6
Applicable income taxes	0	(1)
Ending Balance	$ (10)	$ (23)