Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value
Less than 12 months	$ 1,707	$ 2,253
12 months or more	31,554	32,243
Total	33,261	34,496
Unrealized Losses
Less than 12 months	(21)	(34)
12 months or more	(3,686)	(4,303)
Total	(3,707)	(4,337)
U.S. Treasury and federal agencies securities
Fair Value
Less than 12 months	38	569
12 months or more	0	0
Total	38	569
Unrealized Losses
Less than 12 months	0	0
12 months or more	0	0
Total	0	0
Agency mortgage-backed securities | Residential mortgage backed securities
Fair Value
Less than 12 months	1,196	1,061
12 months or more	4,534	4,566
Total	5,730	5,627
Unrealized Losses
Less than 12 months	(15)	(14)
12 months or more	(636)	(765)
Total	(651)	(779)
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	200	157
12 months or more	20,760	20,536
Total	20,960	20,693
Unrealized Losses
Less than 12 months	(4)	(6)
12 months or more	(2,601)	(3,016)
Total	(2,605)	(3,022)
Non-agency commercial mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	152	183
12 months or more	3,519	3,984
Total	3,671	4,167
Unrealized Losses
Less than 12 months	(1)	(3)
12 months or more	(290)	(335)
Total	(291)	(338)
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	121	283
12 months or more	2,741	3,157
Total	2,862	3,440
Unrealized Losses
Less than 12 months	(1)	(11)
12 months or more	(159)	(187)
Total	$ (160)	$ (198)