Investment Securities - Available-For-Sale Securities (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		$ 94,121	$ 92,793
Unrealized Gains		295	58
Unrealized Losses		(5,351)	(6,859)
Fair Value	[1]	89,065	85,992
Portfolio level basis adjustments, Amortized Cost		304	13
Portfolio level basis adjustments, Unrealized Losses		(304)	(13)
U.S. Treasury and agencies
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		28,556	30,467
Unrealized Gains		10	1
Unrealized Losses		(1,498)	(2,081)
Fair Value		27,068	28,387
Residential mortgage-backed securities | Agency
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		38,921	35,558
Unrealized Gains		245	13
Unrealized Losses		(1,489)	(2,290)
Fair Value		37,677	33,281
Commercial mortgage-backed securities | Agency
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		8,655	8,673
Unrealized Gains		0	0
Unrealized Losses		(961)	(1,322)
Fair Value		7,694	7,351
Commercial mortgage-backed securities | Non-agency
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		7	7
Unrealized Gains		0	0
Unrealized Losses		0	(1)
Fair Value		7	6
Asset-backed securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		6,842	7,136
Unrealized Gains		23	30
Unrealized Losses		0	(1)
Fair Value		6,865	7,165
Obligations of state and political subdivisions
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		10,571	10,690
Unrealized Gains		14	13
Unrealized Losses		(1,099)	(1,151)
Fair Value		9,486	9,552
Other
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		265	249
Unrealized Gains		3	1
Unrealized Losses		0	0
Fair Value		268	250
Excluding portfolio level basis adjustments
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		93,817	92,780
Unrealized Gains		295	58
Unrealized Losses		(5,047)	(6,846)
Fair Value		$ 89,065	$ 85,992

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.