Loans and Allowance for Credit Losses - Investments by Credit Quality (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	$ 36,631	$ 32,145
Financing receivable, held-for-sale		5
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	32,024	27,176
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	3,995	4,491
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	304	379
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	238	99
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	70
Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	33,562	29,160
Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	29,737	24,667
Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	3,546	4,103
Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	242	291
Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	14	99
Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	23
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	3,069	2,985
Commercial real estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	2,287	2,509
Commercial real estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	449	388
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	62	88
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	224	0
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	47
Geographic Distribution, Domestic | Commercial and Financial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	19,995	18,258
Geographic Distribution, Domestic | Commercial and Financial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	17,479	14,986
Geographic Distribution, Domestic | Commercial and Financial | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	2,309	2,943
Geographic Distribution, Domestic | Commercial and Financial | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	184	244
Geographic Distribution, Domestic | Commercial and Financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale		85
Geographic Distribution, Domestic | Commercial and Financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	23
Geographic Distribution, Domestic | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	3,069	2,985
Geographic Distribution, Domestic | Commercial real estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	2,287	2,508
Geographic Distribution, Domestic | Commercial real estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	449	388
Geographic Distribution, Domestic | Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	62	89
Geographic Distribution, Domestic | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	224
Geographic Distribution, Domestic | Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, gross, excluding loans classified as held-for-sale	47
Geographic Distribution, Domestic | Loans to investment funds
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	2,270	$ 2,800
Geographic Distribution, Domestic | Loans to investment funds | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	2,150
Geographic Distribution, Domestic | Loans to investment funds | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Overdrafts	$ 120