Loans and Allowance for Credit Losses - Investments by Credit Quality (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 41,961	$ 36,631
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	36,577	32,024
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,705	3,995
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	276	304
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	211	238
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	192	70
Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	39,105	33,562
Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	34,566	29,737
Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	4,246	3,546
Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	214	242
Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	79	14
Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	0	23
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,856	3,069
Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,011	2,287
Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	459	449
Commercial Real Estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	62	62
Commercial Real Estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	132	224
Commercial Real Estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	192	47
Domestic | Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	22,017	19,995
Domestic | Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	19,066	17,479
Domestic | Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,764	2,309
Domestic | Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	147	184
Domestic | Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	40	23
Domestic | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,856	3,069
Domestic | Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,011	2,287
Domestic | Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	459	449
Domestic | Commercial Real Estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	62	62
Domestic | Commercial Real Estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	132	224
Domestic | Commercial Real Estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	192	47
Domestic | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,500	$ 2,270
Domestic | Fund Finance | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,110
Domestic | Fund Finance | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	$ 390