Loans and Allowance for Credit Losses - Investments by Credit Quality (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 35,429	$ 32,145
Financing receivable, held-for-sale	7	5
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	30,595	27,176
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,352	4,491
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	367	379
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	39	99
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	76
Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	32,312	29,160
Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	28,160	24,667
Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,816	4,103
Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	268	291
Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	39	99
Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	29
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,117	2,985
Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,435	2,509
Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	536	388
Commercial Real Estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	99	88
Commercial Real Estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Commercial Real Estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	47
Domestic | Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	18,384	18,258
Domestic | Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	15,668	14,986
Domestic | Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,450	2,943
Domestic | Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	212	244
Domestic | Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	25	85
Domestic | Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	29
Domestic | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,117	2,985
Domestic | Commercial Real Estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,435	2,508
Domestic | Commercial Real Estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	536	388
Domestic | Commercial Real Estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	99	89
Domestic | Commercial Real Estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total	47
Domestic | Fund Finance
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,590	$ 2,800
Domestic | Fund Finance | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	3,210
Domestic | Fund Finance | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	$ 380