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Regulatory and Capital Adequacy - Additional Information (Details) - USD ($) $ in Millions | 12 Months Ended | 36 Months Ended
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2021 | Dec. 31, 2025
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Regulatory capital adjustments, net of tax, CECL transition |  | $ 2,400 |
Regulatory capital adjustments, net of tax, CECL transition, phased in amount per year | $ 600 |  |
Common equity tier one capital ratio, CECL transition | 12.90% |  |
Common equity tier one capital ratio, excluding CECL transition adjustment | 12.60% |  |
Forecast |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Regulatory capital adjustments, net of tax, CECL transition, phased in amount |  |  | $ 1,200
Capital One Bank (USA), N.A. |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |
Funds available for dividend payments | $ 5,200 |  |

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