Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Available-for-sale securities
Less than 12 months, Fair value	$ 25,632	$ 26,764
Less than 12 months, Gross unrealized losses	645	482
12 months or more, Fair Value	12,592	9,340
12 months or more, Gross unrealized losses	772	689
Total fair value	38,224	36,104
Total gross unrealized losses	1,417	1,171
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	423	2,268
Less than 12 months, Gross unrealized losses	0	14
12 months or more, Fair Value	1,713	2,139
12 months or more, Gross unrealized losses	64	106
Total fair value	2,136	4,407
Total gross unrealized losses	64	120
U.S. GSEs and government agencies mortgage-backed securities
Available-for-sale securities
Total fair value	2,600	5,300
Residential: U.S. Mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	2	1,505
Less than 12 months, Gross unrealized losses	0	6
12 months or more, Fair Value	924	925
12 months or more, Gross unrealized losses	24	44
Total fair value	926	2,430
Total gross unrealized losses	24	50
Residential: Non-U.S. mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	0	0
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	21	30
12 months or more, Gross unrealized losses	0	0
Total fair value	21	30
Total gross unrealized losses	0	0
Commercial mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	421	763
Less than 12 months, Gross unrealized losses	0	8
12 months or more, Fair Value	768	1,184
12 months or more, Gross unrealized losses	40	62
Total fair value	1,189	1,947
Total gross unrealized losses	40	70
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	11,905	10,037
Less than 12 months, Gross unrealized losses	558	233
12 months or more, Fair Value	3,583	2,412
12 months or more, Gross unrealized losses	402	301
Total fair value	15,488	12,449
Total gross unrealized losses	960	534
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	12,559	14,234
Less than 12 months, Gross unrealized losses	87	234
12 months or more, Fair Value	7,001	4,184
12 months or more, Gross unrealized losses	298	270
Total fair value	19,560	18,418
Total gross unrealized losses	385	504
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	0	9
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	0	30
12 months or more, Gross unrealized losses	0	1
Total fair value	0	39
Total gross unrealized losses	0	1
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	584	2
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	163	375
12 months or more, Gross unrealized losses	1	3
Total fair value	747	377
Total gross unrealized losses	1	3
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	161	214
Less than 12 months, Gross unrealized losses	0	1
12 months or more, Fair Value	132	200
12 months or more, Gross unrealized losses	7	8
Total fair value	293	414
Total gross unrealized losses	$ 7	$ 9