Loans and Allowance for Credit Losses - Investments by Credit Quality (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 39,368	$ 36,631
Financing receivable, held-for-sale	8
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	34,850	32,024
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,884	3,995
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	277	304
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	164	238
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	193	70
Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	36,510	33,562
Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	32,734	29,737
Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,529	3,546
Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	215	242
Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	32	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	2,858	3,069
Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,116	2,287
Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	355	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	193	47
Domestic | Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	20,514	19,995
Domestic | Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	17,986	17,479
Domestic | Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,389	2,309
Domestic | Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	121	184
Domestic | Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	18	23
Domestic | Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	0
Domestic | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,857	3,069
Domestic | Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	2,115	2,287
Domestic | Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	355	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	193	47
Domestic | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,670	$ 2,270
Domestic | Fund Finance | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,520
Domestic | Fund Finance | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	$ 140