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Fair Value of Assets and Liabilities - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Segment Reporting Information [Line Items] |  |  |
Gain/(loss) on instrument specific credit risk | $ 0.4 | $ 0.2 | $ 0.5
Disposition of Acquired Properties | Corporate |  |  |
Segment Reporting Information [Line Items] |  |  |
Long-lived asset impairment | 4.6 | 3.9 | 3.0
Reversed asset impairment charges | 0.7 | $ 1.5 |
Disposition of Acquired Properties | Regional Banking |  |  |
Segment Reporting Information [Line Items] |  |  |
Long-lived asset impairment |  |  | $ 0.8
2019 Business Optimization | Disposition of Acquired Properties | Corporate |  |  |
Segment Reporting Information [Line Items] |  |  |
Long-lived asset impairment | 1.5 |  |
2019 Business Optimization | Leased Assets | Corporate |  |  |
Segment Reporting Information [Line Items] |  |  |
Long-lived asset impairment | 14.0 |  |
Reversed asset impairment charges | 1.4 |  |
Rebranding Initiative | Leased Assets | Corporate |  |  |
Segment Reporting Information [Line Items] |  |  |
Long-lived asset impairment | $ 7.1 |  |

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