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Statutory Capital and Surplus (Details) | 12 Months Ended |  |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 1 Months Ended | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |
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Dec. 31, 2011 USD ($) | Dec. 31, 2010 USD ($) | Dec. 31, 2011 Swedish kronor SEK | Dec. 31, 2011 OneBeacon USD ($) | Dec. 31, 2010 OneBeacon USD ($) | Dec. 31, 2009 OneBeacon USD ($) | Dec. 31, 2001 OneBeacon rating | Dec. 31, 2011 Sirius group Dividends resulting from reorganization USD ($) | Dec. 31, 2011 Other Operations USD ($) | Dec. 31, 2011 Regulated insurance operations OneBeacon USD ($) | Dec. 31, 2011 Unregulated insurance operations OneBeacon USD ($) | Dec. 31, 2011 OneBeacon Ltd. USD ($) | Dec. 31, 2011 OneBeacon Ltd. OneBeacon USD ($) | Dec. 31, 2011 OneBeacon Ltd. OneBeacon Ordinary dividends USD ($) | Dec. 31, 2011 OneBeacon Ltd. OneBeacon Special dividends USD ($) | Dec. 31, 2011 OneBeacon Ltd. OneBeacon Dividend received by White Mountains USD ($) | Dec. 31, 2011 Sirius International rating | Nov. 30, 2011 Sirius International Sirius group USD ($) | Dec. 31, 2011 Sirius International Sirius group USD ($) | Dec. 31, 2011 Sirius International Sirius group SEK | Dec. 31, 2011 Sirius International Sirius group Sweden USD ($) | Dec. 31, 2011 Sirius America Sirius group USD ($) | Dec. 31, 2010 Sirius America Sirius group USD ($) | Dec. 31, 2009 Sirius America Sirius group USD ($) | Dec. 31, 2011 Central National USD ($) | Dec. 31, 2010 Central National USD ($) | Dec. 31, 2011 Scandinavian Re Sirius group USD ($) | Dec. 31, 2011 White Shoals Re Sirius group USD ($) | Dec. 31, 2011 Sirius Group USD ($) | Dec. 31, 2011 Sirius Group USD ($) | Dec. 31, 2011 Sirius Group Ordinary dividends USD ($) | Dec. 31, 2011 WM Life Re Other Operations USD ($) | Dec. 31, 2011 WM Advisors USD ($) | Dec. 31, 2011 WM Advisors Other Operations USD ($)
Disclosure of statutory capital and surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statutory net income (loss) |  |  |  | $ 119,600,000 | $ 257,200,000 | $ 210,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 101,400,000 | $ 70,200,000 | $ 46,900,000 | $ 100,000 | $ 1,600,000 |  |  |  |  |  |  |  |
Restricted equity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,600,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Statutory capital and surplus |  |  |  | 1,000,000,000 | 1,100,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,100,000,000 |  |  | 533,700,000 | 742,600,000 |  | 13,400,000 | 15,000,000 | 27,600,000 | 15,400,000 |  |  |  | 26,400,000 |  |
Percentage of statutory surplus most recently reported to regulatory authorities that may be paid as dividends without prior approval of regulatory authorities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |
Percentage of prior year statutory surplus that may be paid as dividends without prior approval of regulatory authorities |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount available for dividend distributions without prior approval of regulatory authorities |  |  |  |  |  |  |  |  |  | 103,000,000 |  |  |  |  |  |  |  |  |  |  |  | 53,400,000 |  |  |  |  |  |  |  |  |  |  |  |
Earned surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 75,500,000 |  |  |  |  |  |  |  |  |  |  |  |
Unassigned funds |  |  |  |  |  |  |  |  |  | 700,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Represents dividends paid by OneBeacon's unregulated insurance operating subsidiaries to their immediate parent |  |  |  |  |  |  |  |  |  |  |  |  | 150,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distributions made |  |  |  |  |  |  |  | 425,000,000 |  |  | 4,300,000 |  |  | 79,700,000 | 95,100,000 | 132,000,000 |  |  | 594,000,000 |  |  |  |  |  |  |  |  |  | 169,000,000 |  | 177,000,000 |  | 5,000,000 |
Net unrestricted cash, short-term investments and fixed maturity investments |  |  |  |  |  |  |  |  | 1,554,300,000 |  | 183,000,000 |  | 16,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 75,100,000 |  |  |  | 25,800,000
Number of ratings in A.M. Best ratings |  |  |  |  |  |  | 15 |  |  |  |  |  |  |  |  |  | 15 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common equity securities and other long-term investments |  |  |  |  |  |  |  |  |  |  | 30,000,000 | 30,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  |  |  |  |  |  |  | 316,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other long-term investments | 301,300,000 | 372,100,000 |  |  |  |  |  |  | 33,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,300,000 |  |  |  |
Increase in unrestricted statutory surplus due to reorganization |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 436,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Exchange rate |  |  | 6.86 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2010 pre-tax income transferred to parent company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 74,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2011 pre-tax income intended to be transferred to parent company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 80,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unrestricted statutory surplus available for distribution |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 514,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends intended to pay to the immediate parent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 177,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other long-term investments outside of Sirius America and Sirius International | 301,300,000 | 372,100,000 |  |  |  |  |  |  | 33,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,300,000 |  |  |  |
Safety Reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of safety reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,400,000,000 | 9,600,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of Deferred Tax Liabilities on Safety Reserve | $ 369,600,000 | $ 378,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 369,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Swedish tax rate (as a percent) | 26.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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