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Basis of Presentation and Accounting Policies (Details) - USD ($) |  | 3 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
May 04, 2023 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Jun. 30, 2023 | Jan. 01, 2023 | Dec. 31, 2022 | Jun. 30, 2022 | Dec. 31, 2021
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for loan and lease losses |  | $ (760,000,000) | $ (664,000,000) | $ (760,000,000) | $ (664,000,000) | $ (737,000,000) |  | $ (685,000,000) | $ (624,000,000) | $ (670,000,000)
Retained earnings |  | 3,874,000,000 |  | 3,874,000,000 |  |  |  | 3,430,000,000 |  |
Accounting Standards Update 2022-02 |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  |  |  |  |  | $ 6,000,000 | $ 6,000,000 |  |
Retained earnings |  |  |  |  |  |  | $ 4,000,000 |  |  |
TD Transaction |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from merger contract termination | $ 200,000,000 |  |  |  |  |  |  |  |  |
Fee reimbursement received | $ 25,000,000 |  |  |  |  |  |  |  |  |
Merger and integration expense |  | $ 0 | $ 21,000,000 | $ 51,000,000 | $ 55,000,000 |  |  |  |  |

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