Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Available-for-sale securities
Less than 12 months, Fair value	$ 10,737	$ 20,904
Less than 12 months, Gross unrealized losses	49	846
12 months or more, Fair value	16,033	8,519
12 months or more, Gross unrealized losses	866	746
Total fair value	26,770	29,423
Total gross unrealized losses	915	1,592
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	309	5,166
Less than 12 months, Gross unrealized losses	3	170
12 months or more, Fair value	3,657	1,143
12 months or more, Gross unrealized losses	205	123
Total fair value	3,966	6,309
Total gross unrealized losses	208	293
U.S. GSEs and government agencies
Available-for-sale securities
Total fair value	4,600	9,600
Residential: U.S.
Available-for-sale securities
Less than 12 months, Fair value	81	1,187
Less than 12 months, Gross unrealized losses	0	71
12 months or more, Fair value	1,160	260
12 months or more, Gross unrealized losses	68	40
Total fair value	1,241	1,447
Total gross unrealized losses	68	111
Residential: Non-U.S.
Available-for-sale securities
Less than 12 months, Fair value	0	2,848
Less than 12 months, Gross unrealized losses	0	25
12 months or more, Fair value	722	70
12 months or more, Gross unrealized losses	1	2
Total fair value	722	2,918
Total gross unrealized losses	1	27
Commercial
Available-for-sale securities
Less than 12 months, Fair value	228	1,131
Less than 12 months, Gross unrealized losses	3	74
12 months or more, Fair value	1,775	813
12 months or more, Gross unrealized losses	136	81
Total fair value	2,003	1,944
Total gross unrealized losses	139	155
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	2,134	3,051
Less than 12 months, Gross unrealized losses	20	241
12 months or more, Fair value	2,278	364
12 months or more, Gross unrealized losses	246	162
Total fair value	4,412	3,415
Total gross unrealized losses	266	403
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	7,145	6,941
Less than 12 months, Gross unrealized losses	23	321
12 months or more, Fair value	4,987	3,848
12 months or more, Gross unrealized losses	336	357
Total fair value	12,132	10,789
Total gross unrealized losses	359	678
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	9	150
Less than 12 months, Gross unrealized losses	0	2
12 months or more, Fair value	79	207
12 months or more, Gross unrealized losses	28	22
Total fair value	88	357
Total gross unrealized losses	28	24
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	932	3,010
Less than 12 months, Gross unrealized losses	2	61
12 months or more, Fair value	3,744	2,701
12 months or more, Gross unrealized losses	26	64
Total fair value	4,676	5,711
Total gross unrealized losses	28	125
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	208	2,586
Less than 12 months, Gross unrealized losses	1	51
12 months or more, Fair value	1,288	256
12 months or more, Gross unrealized losses	25	18
Total fair value	1,496	2,842
Total gross unrealized losses	$ 26	$ 69