Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Available-for-sale securities
Less than 12 months, Fair value	$ 46,606	$ 16,015
Less than 12 months, Gross unrealized losses	572	219
12 months or more, Fair Value	16,154	16,030
12 months or more, Gross unrealized losses	1,182	876
Total fair value	62,760	32,045
Total gross unrealized losses	1,754	1,095
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	2,018	181
Less than 12 months, Gross unrealized losses	7	1
12 months or more, Fair Value	1,069	1,205
12 months or more, Gross unrealized losses	40	46
Total fair value	3,087	1,386
Total gross unrealized losses	47	47
U.S. GSEs and government agencies mortgage-backed securities
Available-for-sale securities
Total fair value	2,900	2,200
Residential: U.S. Mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	904	36
Less than 12 months, Gross unrealized losses	4	0
12 months or more, Fair Value	576	609
12 months or more, Gross unrealized losses	18	17
Total fair value	1,480	645
Total gross unrealized losses	22	17
Residential: Non-U.S. mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	0	3
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	19	20
12 months or more, Gross unrealized losses	0	0
Total fair value	19	23
Total gross unrealized losses	0	0
Commercial mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	1,114	142
Less than 12 months, Gross unrealized losses	3	1
12 months or more, Fair Value	474	576
12 months or more, Gross unrealized losses	22	29
Total fair value	1,588	718
Total gross unrealized losses	25	30
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	4,404	5,519
Less than 12 months, Gross unrealized losses	120	131
12 months or more, Fair Value	10,131	9,597
12 months or more, Gross unrealized losses	936	662
Total fair value	14,535	15,116
Total gross unrealized losses	1,056	793
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	33,805	9,324
Less than 12 months, Gross unrealized losses	428	76
12 months or more, Fair Value	4,694	4,954
12 months or more, Gross unrealized losses	199	160
Total fair value	38,499	14,278
Total gross unrealized losses	627	236
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	117	114
Less than 12 months, Gross unrealized losses	8	11
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	117	114
Total gross unrealized losses	8	11
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	6,182	814
Less than 12 months, Gross unrealized losses	8	0
12 months or more, Fair Value	139	143
12 months or more, Gross unrealized losses	1	1
Total fair value	6,321	957
Total gross unrealized losses	9	1
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	80	63
Less than 12 months, Gross unrealized losses	1	0
12 months or more, Fair Value	121	131
12 months or more, Gross unrealized losses	6	7
Total fair value	201	194
Total gross unrealized losses	$ 7	$ 7