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Fair Value of Assets & Liabilities - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Jun. 30, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Segment Reporting Information [Line Items] |  |  |  |  |  |
Gain/(loss) on instrument specific credit risk | $ 0.0 |  |  | $ 0.1 | $ 0.3 | $ 0.5
Corporate |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Long-lived asset impairment | (0.7) | $ (1.3) | $ (3.0) | $ (2.0) |  |
Reversed Asset Impairment Charges | $ 1.0 |  |  |  |  |
Regional Banking |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Long-lived asset impairment |  |  | $ (0.8) |  |  |

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- Definition This item represents the estimated amount of gains or losses included in earnings during the period attributable to changes in instrument-specific credit risk arising from loans and other receivables held as assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612 + Details
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