Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Available-for-sale securities
Less than 12 months, Fair value	$ 22,715	$ 10,737
Less than 12 months, Gross unrealized losses	269	49
12 months or more, Fair Value	11,573	16,033
12 months or more, Gross unrealized losses	818	866
Total fair value	34,288	26,770
Total gross unrealized losses	1,087	915
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	512	309
Less than 12 months, Gross unrealized losses	5	3
12 months or more, Fair Value	2,519	3,657
12 months or more, Gross unrealized losses	143	205
Total fair value	3,031	3,966
Total gross unrealized losses	148	208
U.S. GSEs and government agencies mortgage-backed securities
Available-for-sale securities
Total fair value	4,900	4,600
Residential: U.S. Mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	114	81
Less than 12 months, Gross unrealized losses	1	0
12 months or more, Fair Value	1,026	1,160
12 months or more, Gross unrealized losses	61	68
Total fair value	1,140	1,241
Total gross unrealized losses	62	68
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	110	722
12 months or more, Gross unrealized losses	0	1
Total fair value	110	722
Total gross unrealized losses	0	1
Commercial mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	398	228
Less than 12 months, Gross unrealized losses	4	3
12 months or more, Fair Value	1,383	1,775
12 months or more, Gross unrealized losses	82	136
Total fair value	1,781	2,003
Total gross unrealized losses	86	139
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	8,602	2,134
Less than 12 months, Gross unrealized losses	184	20
12 months or more, Fair Value	3,003	2,278
12 months or more, Gross unrealized losses	306	246
Total fair value	11,605	4,412
Total gross unrealized losses	490	266
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	13,262	7,145
Less than 12 months, Gross unrealized losses	80	23
12 months or more, Fair Value	4,762	4,987
12 months or more, Gross unrealized losses	339	336
Total fair value	18,024	12,132
Total gross unrealized losses	419	359
Corporate debt securities
Available-for-sale securities
Less than 12 months, Fair value	4	9
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	52	79
12 months or more, Gross unrealized losses	12	28
Total fair value	56	88
Total gross unrealized losses	12	28
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	0	932
Less than 12 months, Gross unrealized losses	0	2
12 months or more, Fair Value	615	3,744
12 months or more, Gross unrealized losses	7	26
Total fair value	615	4,676
Total gross unrealized losses	7	28
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	335	208
Less than 12 months, Gross unrealized losses	0	1
12 months or more, Fair Value	622	1,288
12 months or more, Gross unrealized losses	11	25
Total fair value	957	1,496
Total gross unrealized losses	$ 11	$ 26