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Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 12, 2020 USD ($) $ / shares shares | Dec. 31, 2023 shares | Apr. 25, 2023 shares | Apr. 24, 2023 shares | Dec. 31, 2022 shares | Jan. 03, 2022
Class of Stock [Line Items] |  |  |  |  |  |
Depositary shares, shares issued (in shares) | 13,800,000 |  |  |  |  |
Depository Shares, percentage of preferred stock | 0.025 |  |  |  |  |
Depository shares, equivalent value per preferred share | $ / shares | $ 1,000 |  |  |  |  |
Depositary shares, shares issued, value | $ | $ 345 |  |  |  |  |
Preferred stock, shares authorized (in shares) |  | 20,000,000 | 20,000,000 | 10,000,000 | 10,000,000 |
Class A |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Common stock, voting right per share |  | 1 |  |  |  |
Common stock, shares authorized (in shares) |  | 32,000,000 | 32,000,000 | 16,000,000 | 16,000,000 |
Class B |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Common stock, voting right per share |  | 16 |  |  |  |
Common stock, shares authorized (in shares) |  | 2,000,000 |  |  | 2,000,000 |
Depositary Shares, Each Representing a 1/40th Interest in a Share of 5.375% Non-Cumulative Perpetual Preferred Stock, Series A |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Dividend | 5.375% | 5.375% |  |  |  |
Preferred stock, shares authorized (in shares) |  | 345,000 |  |  |  |
Series B Preferred Stock |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Preferred stock, shares authorized (in shares) |  | 325,000 |  |  |  |
Series B Preferred Stock | CIT Group Inc. |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Common stock, terms of conversion, conversion ratio |  |  |  |  |  | 1
Series C Preferred Stock |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Dividend |  | 5.625% |  |  |  |
Preferred stock, shares authorized (in shares) |  | 8,000,000 |  |  |  |
Series C Preferred Stock | CIT Group Inc. |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |
Common stock, terms of conversion, conversion ratio |  |  |  |  |  | 1

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