Investment Securities - Fair Value and Gross Unrealized Losses by Aging Category (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Available-for-sale securities
Less than 12 months, Fair value	$ 9,229	$ 10,737
Less than 12 months, Gross unrealized losses	62	49
12 months or more, Fair Value	9,965	16,033
12 months or more, Gross unrealized losses	617	866
Total fair value	19,194	26,770
Total gross unrealized losses	679	915
Total mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	274	309
Less than 12 months, Gross unrealized losses	2	3
12 months or more, Fair Value	2,279	3,657
12 months or more, Gross unrealized losses	105	205
Total fair value	2,553	3,966
Total gross unrealized losses	107	208
U.S. GSEs and government agencies mortgage-backed securities
Available-for-sale securities
Total fair value	2,700	4,600
Residential: U.S. Mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	110	81
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	975	1,160
12 months or more, Gross unrealized losses	33	68
Total fair value	1,085	1,241
Total gross unrealized losses	33	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	0	722
12 months or more, Gross unrealized losses	0	1
Total fair value	0	722
Total gross unrealized losses	0	1
Commercial mortgage-backed securities
Available-for-sale securities
Less than 12 months, Fair value	164	228
Less than 12 months, Gross unrealized losses	2	3
12 months or more, Fair Value	1,304	1,775
12 months or more, Gross unrealized losses	72	136
Total fair value	1,468	2,003
Total gross unrealized losses	74	139
Obligations of U.S. states and municipalities
Available-for-sale securities
Less than 12 months, Fair value	1,931	2,134
Less than 12 months, Gross unrealized losses	19	20
12 months or more, Fair Value	2,337	2,278
12 months or more, Gross unrealized losses	228	246
Total fair value	4,268	4,412
Total gross unrealized losses	247	266
Non-U.S. government debt securities
Available-for-sale securities
Less than 12 months, Fair value	6,510	7,145
Less than 12 months, Gross unrealized losses	41	23
12 months or more, Fair Value	4,500	4,987
12 months or more, Gross unrealized losses	262	336
Total fair value	11,010	12,132
Total gross unrealized losses	303	359
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	17	79
12 months or more, Gross unrealized losses	9	28
Total fair value	17	88
Total gross unrealized losses	9	28
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Less than 12 months, Fair value	395	932
Less than 12 months, Gross unrealized losses	0	2
12 months or more, Fair Value	516	3,744
12 months or more, Gross unrealized losses	5	26
Total fair value	911	4,676
Total gross unrealized losses	5	28
Asset-backed securities: Other
Available-for-sale securities
Less than 12 months, Fair value	119	208
Less than 12 months, Gross unrealized losses	0	1
12 months or more, Fair Value	316	1,288
12 months or more, Gross unrealized losses	8	25
Total fair value	435	1,496
Total gross unrealized losses	$ 8	$ 26