Loans and Allowance for Credit Losses - Amortized Cost Basis (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 8,247	$ 5,572
Fiscal year before current fiscal year	2,871	3,020
Two years before current fiscal year	2,105	4,685
Three years before current fiscal year	3,722	424
Four years before current fiscal year	336	1,229
Prior	2,033	1,291
Revolving Loans	22,647	20,410
Total	41,961	36,631
Accrued interest receivable	309	318
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	36,577	32,024
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,705	3,995
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	276	304
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	211	238
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	192	70
Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	39,105	33,562
Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	34,566	29,737
Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,246	3,546
Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	214	242
Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	79	14
Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	23
Commercial and Financial | Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,599	2,019
Fiscal year before current fiscal year	432	409
Two years before current fiscal year	222	1,128
Three years before current fiscal year	595	157
Four years before current fiscal year	59	579
Prior	482	146
Revolving Loans	16,628	15,557
Total	22,017	19,995
Commercial and Financial | Domestic | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,933	1,399
Fiscal year before current fiscal year	223	120
Two years before current fiscal year	64	199
Three years before current fiscal year	47	8
Four years before current fiscal year	6	272
Prior	250	5
Revolving Loans	16,543	15,476
Total	19,066	17,479
Commercial and Financial | Domestic | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,603	615
Fiscal year before current fiscal year	168	285
Two years before current fiscal year	147	747
Three years before current fiscal year	476	149
Four years before current fiscal year	53	291
Prior	232	141
Revolving Loans	85	81
Total	2,764	2,309
Commercial and Financial | Domestic | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	49	0
Fiscal year before current fiscal year	41	4
Two years before current fiscal year	0	164
Three years before current fiscal year	57	0
Four years before current fiscal year	0	16
Prior	0	0
Revolving Loans	0	0
Total	147	184
Commercial and Financial | Domestic | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	14	5
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	11	18
Three years before current fiscal year	15	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans	0	0
Total	40	23
Commercial and Financial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	4,607	3,337
Fiscal year before current fiscal year	2,224	2,091
Two years before current fiscal year	1,363	3,028
Three years before current fiscal year	2,779	117
Four years before current fiscal year	49	109
Prior	47	32
Revolving Loans	6,019	4,853
Total	17,088	13,567
Commercial and Financial | Non-U.S. | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	3,992	2,943
Fiscal year before current fiscal year	2,004	1,956
Two years before current fiscal year	1,287	2,518
Three years before current fiscal year	2,415	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans	5,802	4,841
Total	15,500	12,258
Commercial and Financial | Non-U.S. | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	615	394
Fiscal year before current fiscal year	182	135
Two years before current fiscal year	76	481
Three years before current fiscal year	296	88
Four years before current fiscal year	49	109
Prior	47	18
Revolving Loans	217	12
Total	1,482	1,237
Commercial and Financial | Non-U.S. | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	38	0
Two years before current fiscal year	0	29
Three years before current fiscal year	29	29
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans	0	0
Total	67	58
Commercial and Financial | Non-U.S. | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	39	0
Four years before current fiscal year	0	0
Prior	0	14
Revolving Loans	0	0
Total	39	14
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,856	3,069
Commercial real estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,011	2,287
Commercial real estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	459	449
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	62	62
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	132	224
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	192	47
Commercial real estate | Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	41	216
Fiscal year before current fiscal year	215	520
Two years before current fiscal year	520	529
Three years before current fiscal year	348	150
Four years before current fiscal year	228	541
Prior	1,504	1,113
Revolving Loans	0	0
Total	2,856	3,069
Commercial real estate | Domestic | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	41	216
Fiscal year before current fiscal year	92	500
Two years before current fiscal year	500	498
Three years before current fiscal year	278	100
Four years before current fiscal year	128	375
Prior	972	598
Revolving Loans	0	0
Total	2,011	2,287
Commercial real estate | Domestic | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	123	20
Two years before current fiscal year	20	31
Three years before current fiscal year	70	50
Four years before current fiscal year	100	49
Prior	146	299
Revolving Loans	0	0
Total	459	449
Commercial real estate | Domestic | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	22
Prior	62	40
Revolving Loans	0	0
Total	62	62
Commercial real estate | Domestic | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	95
Prior	132	129
Revolving Loans	0	0
Total	132	224
Commercial real estate | Domestic | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	192	47
Revolving Loans	0	0
Total	$ 192	$ 47