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Business Combinations - Narrative (Details) |  | 12 Months Ended
--- | --- | ---
Jan. 03, 2022 USD ($) $ / shares shares | Dec. 31, 2022 USD ($) $ / shares shares | Dec. 31, 2021 USD ($) $ / shares | Dec. 31, 2020 USD ($)
Business Acquisition [Line Items] |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares |  | $ 0.01 | $ 0.01 |
Preferred stock, non-callable period, extended term | 5 years |  |  |
Gain on acquisition |  | $ 431,000,000 | $ 0 | $ 0
Pro forma adjustment |  | 1,098,000,000 | 547,000,000 | 492,000,000
Merger-related expenses |  | 231,000,000 | $ 29,000,000 | $ 17,000,000
CIT Group Inc. |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Business combination, number of fractional shares purchased (in shares) | shares | 8,800 |  |  |
Business combination, payment to purchase fractional shares | $ 7,000,000 |  |  |
Stock-based compensation consideration | 81,000,000 |  |  |
Gain on acquisition | 431,000,000 |  |  |
Initial PCD ACL | $ 272,000,000 |  |  |
Business combination, pro forma information, earnings or loss of acquiree since acquisition date, actual |  | 587,000,000 |  |
CIT Group Inc. | Provision for Credit Losses |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Pro forma adjustment |  | 513,000,000 |  |
CIT Group Inc. | Interest income |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Business combination, pro forma information, revenue of acquiree since acquisition date, actual |  | 1,750,000,000 |  |
CIT Group Inc. | Noninterest income |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Business combination, pro forma information, revenue of acquiree since acquisition date, actual |  | $ 1,240,000,000 |  |
Class A Common Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Common stock, par value (in dollars per share) | $ / shares | $ 1.00 | $ 1 | $ 1 |
Class A Common Stock | CIT Group Inc. |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Common stock, terms of conversion, conversion ratio | 0.062 |  |  |
Business acquisition, equity interest Issued or issuable (in shares) | shares | 6,140,010 |  |  |
Sale of stock (in dollars per share) | $ / shares | $ 859.76 |  |  |
Equity consideration | $ 5,279,000,000 |  |  |
Series A Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares |  | $ 0.01 |  |
Preferred stock, dividend rate |  | 5.375% |  |
Preferred stock, shares outstanding (in shares) | shares |  | 345,000 |  |
Liquidation preference per share (in dollars per share) | $ / shares |  | $ 1,000 |  |
Total Liquidation Preference |  | $ 345,000,000 |  |
Series B Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares |  | $ 0.01 |  |
Preferred stock, dividend rate |  | 5.80% |  |
Preferred stock, shares outstanding (in shares) | shares | 325,000 | 325,000 |  |
Liquidation preference per share (in dollars per share) | $ / shares | $ 1,000 | $ 1,000 |  |
Total Liquidation Preference | $ 325,000,000 | $ 325,000,000 |  |
Series C Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares |  | $ 0.01 |  |
Preferred stock, dividend rate |  | 5.625% |  |
Preferred stock, shares outstanding (in shares) | shares | 8,000,000 | 8,000,000 |  |
Liquidation preference per share (in dollars per share) | $ / shares | $ 25 | $ 25 |  |
Total Liquidation Preference | $ 200,000,000 | $ 200,000,000 |  |
Preferred Stock | CIT Group Inc. |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Equity consideration | $ 541,000,000 |  |  |
CIT Group Inc. |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Common stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |
CIT Group Inc. | Series A Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |
CIT Group Inc. | Series B Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Common stock, terms of conversion, conversion ratio | 1 |  |  |
Preferred stock, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |
Preferred stock, dividend rate | 5.625% |  |  |
CIT Group Inc. | Series C Preferred Stock |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Common stock, terms of conversion, conversion ratio | 1 |  |  |

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