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Contingencies (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended | 60 Months Ended |
--- | --- | --- | --- | --- | ---
Jun. 30, 2007 | Sep. 30, 2016 | Jun. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Oct. 07, 2011
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  |  |  | $ 414.5 | $ 18.2 |  |
Esurance |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Percentage of fluctuation in loss reserves of transferred subsidiaries retained |  |  |  |  |  |  |  | 90.00%
Tribune Company Litigation | Pending Litigation | OneBeacon [Member] |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Proceeds from Sale, Maturity and Collection of Investments | $ 32.0 |  |  |  |  |  |  |
Discontinued Operations [Member] |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  | $ 14.0 |  | $ (3.8) | 7.1 | 59.1 |  |
Esurance |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  |  | 10.3 |  | 18.2 |  |
Esurance | Discontinued Operations [Member] |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  | 10.3 |  | 10.3 |  | 17.9 | $ 28.3 |
OneBeacon Runoff [Member] | Discontinued Operations [Member] |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  |  |  |  | 0.3 |  |
Sirius Group |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  | $ (4.0) | $ 366.6 | 0.0 | 362.6 | 0.0 |  |
Sirius Group | Discontinued Operations [Member] |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  | $ 0.0 | $ 4.0 | $ (6.4) | $ 73.7 |  |

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