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Discontinued Operations - Interest Rate Cap (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Jul. 31, 2013 | May. 31, 2007 | Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2013 | Jun. 30, 2015 | Sep. 30, 2015 | Sep. 30, 2014
Preferred Stock [Member] | Sirius Group |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |
Preferred Stock, Dividend Rate, Percentage |  | 7.506% |  |  |  |  |  |
Interest Rate Cap [Member] | Sirius Group |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |
Years of interest rate cap |  |  |  |  | 5 years |  |  |
Derivative, Cap Interest Rate | 8.30% |  |  |  |  |  |  |
Derivative, Cost of Hedge | $ 9.9 |  |  |  |  |  |  |
Beginning of period |  |  | $ 3.3 | $ 6.2 |  | $ 4.1 | $ 4.1 | $ 11.1
Realized and unrealized gains (losses) |  |  | (1.1) | (0.8) |  |  | (1.9) | (5.7)
End of period |  |  | $ 2.2 | $ 5.4 |  | $ 3.3 | $ 2.2 | $ 5.4
Interest Rate Cap [Member] | Preferred Stock [Member] | Sirius Group |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction | 250,000,000.0 |  |  |  |  |  |  |
Sirius Group Ltd [Member] | Preferred Stock [Member] |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |
Term of LIBOR loan |  | 3 months |  |  |  |  |  |
Basis points |  | 3.20% |  |  |  |  |  |
Sirius Group Ltd [Member] | Interest Rate Cap [Member] |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |
Basis points | 3.95% |  |  |  |  |  |  |

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