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Discontinued Operations (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 48 Months Ended
--- | --- | --- | ---
Sep. 30, 2015 | Jun. 30, 2015 | Sep. 30, 2014 | Jun. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015
Discontinued Operations [Line Items} |  |  |  |  |  |  |
Net gain on sale of discontinued operations | $ 10.3 |  | $ 7.0 |  | $ 18.2 | $ 9.7 |
Net income from discontinued operations, net of tax | 3.9 |  | 56.9 |  | 73.3 | 166.8 |
Net Realized and Unrealized Gain (Loss) on Trading Securities | (43.9) |  | (27.5) |  | (33.9) | 64.4 |
Sirius Group |  |  |  |  |  |  |
Discontinued Operations [Line Items} |  |  |  |  |  |  |
Investment Income, Net | 5.5 |  | 0.9 |  | 1.4 | 1.8 |
Net Realized and Unrealized Gain (Loss) on Trading Securities | 5.5 |  | 0.9 |  | 1.4 | 1.8 |
OneBeacon Runoff [Member] |  |  |  |  |  |  |
Discontinued Operations [Line Items} |  |  |  |  |  |  |
Change in seller financing |  |  |  | $ 6.7 |  |  |
Amount of Seller Financing |  |  |  | 80.9 |  |  |
Surplus Notes |  |  |  | 80.9 |  |  |
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax | 10.3 |  | 10.3 | 8.2 | 18.2 |  | $ 28.3
Net gain on sale of discontinued operations |  |  | 6.7 | 5.3 |  |  |
Reserve charge under the SPA, before tax |  |  |  | 7.4 |  |  |
Transfer of assets |  |  |  | 7.4 |  |  |
Reserve Charge After-Tax |  |  |  | $ 4.8 |  |  |
Proceeds from Sale of Buildings |  | $ 58.0 |  |  |  |  |
Esurance |  |  |  |  |  |  |
Discontinued Operations [Line Items} |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  |  |  |  | $ 3.2 |
Net income from discontinued operations, net of tax | $ 10.3 |  |  |  | $ 18.2 |  |
Fireman's Fund Insurance Company [Member] |  |  |  |  |  |  |
Discontinued Operations [Line Items} |  |  |  |  |  |  |
Net gain on sale of discontinued operations |  |  | $ 14.0 |  |  |  |

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