Investment Securities - Fair Value and Gross Unrealized Losses on Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value
Less than 12 months	$ 2,253	$ 7,990
12 months or more	32,243	40,782
Total	34,496	48,772
Unrealized Losses
Less than 12 months	(34)	(580)
12 months or more	(4,303)	(4,799)
Total	(4,337)	(5,379)
Amortized Cost	11,278	2
U.S. Treasury and federal agencies securities
Fair Value
Less than 12 months	569	1,989
12 months or more	0	2,157
Total	569	4,146
Unrealized Losses
Less than 12 months	0	(3)
12 months or more	0	(139)
Total	0	(142)
Amortized Cost	2,370
Agency mortgage-backed securities | Residential mortgage backed securities
Fair Value
Less than 12 months	1,061	81
12 months or more	4,566	10,200
Total	5,627	10,281
Unrealized Losses
Less than 12 months	(14)	(2)
12 months or more	(765)	(1,280)
Total	(779)	(1,282)
Amortized Cost	4,898
Agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	157	5,439
12 months or more	20,536	19,957
Total	20,693	25,396
Unrealized Losses
Less than 12 months	(6)	(556)
12 months or more	(3,016)	(2,674)
Total	(3,022)	(3,230)
Amortized Cost	4,008
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Fair Value
Less than 12 months	183	141
12 months or more	3,984	4,284
Total	4,167	4,425
Unrealized Losses
Less than 12 months	(3)	(2)
12 months or more	(335)	(425)
Total	(338)	(427)
Asset-backed securities and other debt securities
Fair Value
Less than 12 months	283	340
12 months or more	3,157	4,184
Total	3,440	4,524
Unrealized Losses
Less than 12 months	(11)	(17)
12 months or more	(187)	(281)
Total	(198)	(298)
Amortized Cost	$ 2	$ 2