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Business Combinations and Discontinued Operations - Additional Information (Details) - USD ($) $ in Millions |  | 3 Months Ended | 9 Months Ended | 21 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
May 18, 2025 | Sep. 30, 2025 | Sep. 30, 2025 | Sep. 30, 2025 | Jun. 30, 2025 | Dec. 31, 2024
Business Combination [Line Items] |  |  |  |  |  |
Common stock, shares issued (in shares) |  | 707,690,438 | 707,690,438 | 707,690,438 |  | 702,224,674
Treasury stock, shares (in shares) |  | 71,956,833 | 71,956,833 | 71,956,833 |  | 320,994,331
Preferred stock, shares issued (in shares) |  | 4,980,700 | 4,980,700 | 4,980,700 |  | 4,975,000
Preferred stock, value, issued |  | $ 0 | $ 0 | $ 0 |  | $ 0
Goodwill |  | 28,863 | 28,863 | 28,863 |  | $ 15,059
Series D Preferred Stock |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Per annum dividend rate | 6.125% |  |  |  |  |
Series P |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Per annum dividend rate | 6.125% |  |  |  |  |
Discover |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Common stock, shares issued (in shares) | 1.0192 |  |  |  |  |
Treasury stock, shares (in shares) | 256,497,213 |  |  |  |  |
Treasury stock, value | $ 50,600 |  |  |  |  |
Preferred stock, shares issued (in shares) | 10,700 |  |  |  |  |
Preferred stock, value, issued | $ 1,100 |  |  |  |  |
Business combination, stock-based compensation award | 136 |  |  |  |  |
Fair value of purchase consideration | 51,793 |  |  |  |  |
Launch and integration expenses |  | 348 | 757 | 991 |  |
Business combination, acquisition related costs | 124 |  |  |  |  |
Business combination, provisional information, initial accounting incomplete, adjustment, intangibles |  | 600 |  |  |  |
Business combination, provisional information, initial accounting incomplete, adjustment, property, plant, and equipment |  | 109 |  |  |  |
Business combination, provisional information, initial accounting incomplete, adjustment, deferred income taxes |  | 148 |  |  |  |
Goodwill, measurement period adjustment |  | 536 |  |  |  |
Business combination, allowance for credit losses PCD loan | 8,800 | $ 8,800 | 8,800 | $ 8,800 | $ 8,800 |
Business combination, pro-forma information, interest income from continuing operations |  |  | 5,300 |  |  |
Business combination, pro-forma information, non-interest income from continuing operations |  |  | 1,100 |  |  |
Business combination, pro forma information, pro forma income (loss) from continuing operations, after tax |  |  | $ (5,300) |  |  |
Goodwill | 13,778 |  |  |  |  |
Discover | Credit Card |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Goodwill | 6,800 |  |  |  |  |
Discover | Consumer Banking |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Goodwill | $ 7,000 |  |  |  |  |
Discover | Series P |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Per annum dividend rate | 6.125% |  |  |  |  |
Preferred stock, shares issued (in shares) | 5,000 |  |  |  |  |
Discover | Discover |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |
Common stock, shares issued (in shares) | 251,679,740 |  |  |  |  |

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