Investment Securities - Gross Unrealized Losses and Fair Values of Investments in Continuous Unrealized Loss Positions (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
AFS securities, Fair Value
Less than 12 months	$ 13,357	$ 22,396
12 months or more	28,333	29,690
Total	41,690	52,086
AFS securities, Unrealized Losses
Less than 12 months	(161)	(334)
12 months or more	(5,351)	(6,209)
Total	(5,512)	(6,543)
U.S. Treasury
AFS securities, Fair Value
Less than 12 months	2,731	1,579
12 months or more	242	352
Total	2,973	1,931
AFS securities, Unrealized Losses
Less than 12 months	(21)	(6)
12 months or more	(11)	(18)
Total	(32)	(24)
GSE
AFS securities, Fair Value
Less than 12 months	105	146
12 months or more	208	230
Total	313	376
AFS securities, Unrealized Losses
Less than 12 months	(2)	(4)
12 months or more	(25)	(35)
Total	(27)	(39)
Agency MBS – residential
AFS securities, Fair Value
Less than 12 months	10,300	20,546
12 months or more	25,721	26,788
Total	36,021	47,334
AFS securities, Unrealized Losses
Less than 12 months	(122)	(322)
12 months or more	(4,712)	(5,494)
Total	(4,834)	(5,816)
Debt Securities, Held-to-Maturity, Fair Value
Less than 12 months	0	0
12 months or more	39,611	40,286
Total	39,611	40,286
Debt Securities, Held-To-Maturity, Unrealized Losses
Less than 12 months	0	0
12 months or more	(9,362)	(10,354)
Total	(9,362)	(10,354)
Agency MBS – commercial
AFS securities, Fair Value
Less than 12 months	35	105
12 months or more	2,118	2,111
Total	2,153	2,216
AFS securities, Unrealized Losses
Less than 12 months	0	(1)
12 months or more	(600)	(644)
Total	(600)	(645)
States and political subdivisions
AFS securities, Fair Value
Less than 12 months	178	20
12 months or more	37	202
Total	215	222
AFS securities, Unrealized Losses
Less than 12 months	(16)	(1)
12 months or more	(3)	(18)
Total	(19)	(19)
Other
AFS securities, Fair Value
Less than 12 months	8	0
12 months or more	7	7
Total	15	7
AFS securities, Unrealized Losses
Less than 12 months	0	0
12 months or more	0	0
Total	$ 0	$ 0