Investment Securities - Schedule of Contractual Maturities of Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	$ 8,914
Available for sale, under 1 year, fair value	8,915
Available for sale, 1 to 5 years, amortized cost	27,709
Available for sale, 1 to 5 years, fair value	27,806
Available for sale, 6 to 10 years, amortized cost	10,162
Available for sale, 6 to 10 years, fair value	10,130
Available for sale, over 10 years, amortized cost	9,968
Available for sale, over 10 years, fair value	10,002
Available for sale, amortized cost	56,753	$ 44,853
Available for sale, fair value	56,853	44,526
Held to maturity, amortized cost	49,477	57,117
Investment securities held-to-maturity	44,925	51,503
Direct obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	4,884
Available for sale, under 1 year, fair value	4,890
Available for sale, 1 to 5 years, amortized cost	11,563
Available for sale, 1 to 5 years, fair value	11,545
Available for sale, 6 to 10 years, amortized cost	2,699
Available for sale, 6 to 10 years, fair value	2,689
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	19,146	8,427
Available for sale, fair value	19,124	8,301
Held to maturity, under 1 year, amortized cost	3,520
Held to maturity, under 1 year, fair value	3,487
Held to maturity, 1 to 5 years, amortized cost	2,060
Held to maturity, 1 to 5 years, fair value	2,029
Held to maturity, 6 to 10 years, amortized cost	1
Held to maturity, 6 to 10 years, fair value	1
Held to maturity, over 10 years, amortized cost	8
Held to maturity, over 10 years, fair value	8
Held to maturity, amortized cost	5,589	8,584
Investment securities held-to-maturity	5,525	8,421
Mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	38
Available for sale, under 1 year, fair value	38
Available for sale, 1 to 5 years, amortized cost	2,011
Available for sale, 1 to 5 years, fair value	2,007
Available for sale, 6 to 10 years, amortized cost	2,804
Available for sale, 6 to 10 years, fair value	2,774
Available for sale, over 10 years, amortized cost	6,417
Available for sale, over 10 years, fair value	6,441
Available for sale, amortized cost	11,270	10,870
Available for sale, fair value	11,260	10,755
Held to maturity, under 1 year, amortized cost	137
Held to maturity, under 1 year, fair value	126
Held to maturity, 1 to 5 years, amortized cost	1,329
Held to maturity, 1 to 5 years, fair value	1,246
Held to maturity, 6 to 10 years, amortized cost	3,678
Held to maturity, 6 to 10 years, fair value	3,220
Held to maturity, over 10 years, amortized cost	31,807
Held to maturity, over 10 years, fair value	27,961
Held to maturity, amortized cost	36,951	39,472
Investment securities held-to-maturity	32,553	34,208
Total U.S. Treasury and federal agencies
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	4,922
Available for sale, under 1 year, fair value	4,928
Available for sale, 1 to 5 years, amortized cost	13,574
Available for sale, 1 to 5 years, fair value	13,552
Available for sale, 6 to 10 years, amortized cost	5,503
Available for sale, 6 to 10 years, fair value	5,463
Available for sale, over 10 years, amortized cost	6,417
Available for sale, over 10 years, fair value	6,441
Available for sale, amortized cost	30,416	19,297
Available for sale, fair value	30,384	19,056
Held to maturity, under 1 year, amortized cost	3,657
Held to maturity, under 1 year, fair value	3,613
Held to maturity, 1 to 5 years, amortized cost	3,389
Held to maturity, 1 to 5 years, fair value	3,275
Held to maturity, 6 to 10 years, amortized cost	3,679
Held to maturity, 6 to 10 years, fair value	3,221
Held to maturity, over 10 years, amortized cost	31,815
Held to maturity, over 10 years, fair value	27,969
Held to maturity, amortized cost	42,540	48,056
Investment securities held-to-maturity	38,078	42,629
Mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	127
Available for sale, under 1 year, fair value	128
Available for sale, 1 to 5 years, amortized cost	411
Available for sale, 1 to 5 years, fair value	411
Available for sale, 6 to 10 years, amortized cost	52
Available for sale, 6 to 10 years, fair value	52
Available for sale, over 10 years, amortized cost	1,946
Available for sale, over 10 years, fair value	1,946
Available for sale, amortized cost	2,536	1,861
Available for sale, fair value	2,537	1,857
Asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	349
Available for sale, under 1 year, fair value	347
Available for sale, 1 to 5 years, amortized cost	415
Available for sale, 1 to 5 years, fair value	415
Available for sale, 6 to 10 years, amortized cost	1,083
Available for sale, 6 to 10 years, fair value	1,086
Available for sale, over 10 years, amortized cost	442
Available for sale, over 10 years, fair value	445
Available for sale, amortized cost	2,289	2,148
Available for sale, fair value	2,293	2,137
Non-U.S. sovereign, supranational and non-U.S. agency
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	3,090
Available for sale, under 1 year, fair value	3,087
Available for sale, 1 to 5 years, amortized cost	10,584
Available for sale, 1 to 5 years, fair value	10,653
Available for sale, 6 to 10 years, amortized cost	1,551
Available for sale, 6 to 10 years, fair value	1,549
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	15,225	15,159
Available for sale, fair value	15,289	15,100
Held to maturity, under 1 year, amortized cost	1,524
Held to maturity, under 1 year, fair value	1,511
Held to maturity, 1 to 5 years, amortized cost	2,545
Held to maturity, 1 to 5 years, fair value	2,498
Held to maturity, 6 to 10 years, amortized cost	263
Held to maturity, 6 to 10 years, fair value	255
Held to maturity, over 10 years, amortized cost	0
Held to maturity, over 10 years, fair value	0
Held to maturity, amortized cost	4,332	5,757
Investment securities held-to-maturity	4,264	5,612
Other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	320
Available for sale, under 1 year, fair value	319
Available for sale, 1 to 5 years, amortized cost	2,391
Available for sale, 1 to 5 years, fair value	2,441
Available for sale, 6 to 10 years, amortized cost	131
Available for sale, 6 to 10 years, fair value	136
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	2,842	2,733
Available for sale, fair value	2,896	2,735
Total non-U.S. debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	3,886
Available for sale, under 1 year, fair value	3,881
Available for sale, 1 to 5 years, amortized cost	13,801
Available for sale, 1 to 5 years, fair value	13,920
Available for sale, 6 to 10 years, amortized cost	2,817
Available for sale, 6 to 10 years, fair value	2,823
Available for sale, over 10 years, amortized cost	2,388
Available for sale, over 10 years, fair value	2,391
Available for sale, amortized cost	22,892	21,901
Available for sale, fair value	23,015	21,829
Held to maturity, under 1 year, amortized cost	1,524
Held to maturity, under 1 year, fair value	1,511
Held to maturity, 1 to 5 years, amortized cost	2,545
Held to maturity, 1 to 5 years, fair value	2,498
Held to maturity, 6 to 10 years, amortized cost	263
Held to maturity, 6 to 10 years, fair value	255
Held to maturity, over 10 years, amortized cost	0
Held to maturity, over 10 years, fair value	0
Held to maturity, amortized cost	4,332	5,757
Investment securities held-to-maturity	4,264	5,612
Student loans
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	24
Available for sale, under 1 year, fair value	25
Available for sale, 1 to 5 years, amortized cost	0
Available for sale, 1 to 5 years, fair value	0
Available for sale, 6 to 10 years, amortized cost	12
Available for sale, 6 to 10 years, fair value	12
Available for sale, over 10 years, amortized cost	55
Available for sale, over 10 years, fair value	56
Available for sale, amortized cost	91	113
Available for sale, fair value	93	114
Held to maturity, under 1 year, amortized cost	156
Held to maturity, under 1 year, fair value	153
Held to maturity, 1 to 5 years, amortized cost	283
Held to maturity, 1 to 5 years, fair value	283
Held to maturity, 6 to 10 years, amortized cost	421
Held to maturity, 6 to 10 years, fair value	421
Held to maturity, over 10 years, amortized cost	1,745
Held to maturity, over 10 years, fair value	1,726
Held to maturity, amortized cost	2,605	3,298
Investment securities held-to-maturity	2,583	3,238
Collateralized loan obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	20
Available for sale, under 1 year, fair value	20
Available for sale, 1 to 5 years, amortized cost	151
Available for sale, 1 to 5 years, fair value	151
Available for sale, 6 to 10 years, amortized cost	1,776
Available for sale, 6 to 10 years, fair value	1,778
Available for sale, over 10 years, amortized cost	1,107
Available for sale, over 10 years, fair value	1,109
Available for sale, amortized cost	3,054	2,530
Available for sale, fair value	3,058	2,527
Non-agency CMBS and RMBS
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	0
Available for sale, under 1 year, fair value	0
Available for sale, 1 to 5 years, amortized cost	0
Available for sale, 1 to 5 years, fair value	0
Available for sale, 6 to 10 years, amortized cost	0
Available for sale, 6 to 10 years, fair value	0
Available for sale, over 10 years, amortized cost	1
Available for sale, over 10 years, fair value	5
Available for sale, amortized cost	1	252
Available for sale, fair value	5	249
Held to maturity, amortized cost	0	6
Investment securities held-to-maturity	0	24
Other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	0
Available for sale, under 1 year, fair value	0
Available for sale, 1 to 5 years, amortized cost	90
Available for sale, 1 to 5 years, fair value	91
Available for sale, 6 to 10 years, amortized cost	0
Available for sale, 6 to 10 years, fair value	0
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	90	90
Available for sale, fair value	91	90
Total asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	44
Available for sale, under 1 year, fair value	45
Available for sale, 1 to 5 years, amortized cost	241
Available for sale, 1 to 5 years, fair value	242
Available for sale, 6 to 10 years, amortized cost	1,788
Available for sale, 6 to 10 years, fair value	1,790
Available for sale, over 10 years, amortized cost	1,163
Available for sale, over 10 years, fair value	1,170
Available for sale, amortized cost	3,236	2,985
Available for sale, fair value	3,247	2,980
Held to maturity, under 1 year, amortized cost	156
Held to maturity, under 1 year, fair value	153
Held to maturity, 1 to 5 years, amortized cost	283
Held to maturity, 1 to 5 years, fair value	283
Held to maturity, 6 to 10 years, amortized cost	421
Held to maturity, 6 to 10 years, fair value	421
Held to maturity, over 10 years, amortized cost	1,745
Held to maturity, over 10 years, fair value	1,726
Held to maturity, amortized cost	2,605	3,304
Investment securities held-to-maturity	2,583	3,262
State and political subdivisions
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	30
Available for sale, under 1 year, fair value	30
Available for sale, 1 to 5 years, amortized cost	67
Available for sale, 1 to 5 years, fair value	67
Available for sale, 6 to 10 years, amortized cost	54
Available for sale, 6 to 10 years, fair value	54
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	151	356
Available for sale, fair value	151	355
Other U.S. debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	32
Available for sale, under 1 year, fair value	31
Available for sale, 1 to 5 years, amortized cost	26
Available for sale, 1 to 5 years, fair value	25
Available for sale, 6 to 10 years, amortized cost	0
Available for sale, 6 to 10 years, fair value	0
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	58	314
Available for sale, fair value	56	$ 306
Total
Contractual Maturities Of Debt Investment Securities [Line Items]
Held to maturity, under 1 year, amortized cost	5,337
Held to maturity, under 1 year, fair value	5,277
Held to maturity, 1 to 5 years, amortized cost	6,217
Held to maturity, 1 to 5 years, fair value	6,056
Held to maturity, 6 to 10 years, amortized cost	4,363
Held to maturity, 6 to 10 years, fair value	3,897
Held to maturity, over 10 years, amortized cost	33,560
Held to maturity, over 10 years, fair value	29,695
Held to maturity, amortized cost	49,477
Investment securities held-to-maturity	$ 44,925