Accumulated Other Comprehensive Income (Loss) - Reconciliation of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 56,885	$ 53,484	$ 55,771	$ 51,232
Changes in unrealized gains (losses)	1,297	(1,881)	1,048	(1,036)
Changes in unrealized gains (losses)	460	(349)	8	(610)
Changes in unrealized gains (losses)	0	(1)	0	0
Changes in unrealized gains (losses)	1,757	(2,231)	1,056	(1,646)
Foreign currency translation adjustment	12	3	16	21
Reclassification to earnings of realized (gains) losses	328	170	736	475
Applicable income taxes	(535)	521	(458)	302
Ending Balance	59,321	53,578	59,321	53,578
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(10,308)	(10,718)	(10,096)	(11,407)
Ending Balance	(8,746)	(12,255)	(8,746)	(12,255)
Unrealized Gains (Losses) on Investment Securities Available-for- Sale
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(5,310)	(5,716)	(5,151)	(6,378)
Changes in unrealized gains (losses)	1,297	(1,881)	1,048	(1,036)
Reclassification to earnings of realized (gains) losses	119		153	29
Applicable income taxes	(361)	474	(305)	262
Ending Balance	(4,255)	(7,123)	(4,255)	(7,123)
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	(3,354)	(3,737)	(3,537)	(3,933)
Reclassification to earnings of realized (gains) losses	132	144	377	406
Applicable income taxes	(33)	(37)	(95)	(103)
Ending Balance	(3,255)	(3,630)	(3,255)	(3,630)
Unrealized Gains (Losses) on Derivative Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(482)	(294)	(242)	(114)
Changes in unrealized gains (losses)	460	(349)	8	(610)
Reclassification to earnings of realized (gains) losses	77	28	206	46
Applicable income taxes	(138)	82	(55)	145
Ending Balance	(83)	(533)	(83)	(533)
Unrealized Gains (Losses) on Retirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1,138)	(941)	(1,138)	(939)
Changes in unrealized gains (losses)		1
Reclassification to earnings of realized (gains) losses		(2)		(6)
Applicable income taxes		2		3
Ending Balance	(1,138)	(942)	(1,138)	(942)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(24)	(30)	(28)	(43)
Foreign currency translation adjustment	12	3	16	21
Applicable income taxes	(3)		(3)	(5)
Ending Balance	$ (15)	$ (27)	$ (15)	$ (27)