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Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2010 | Jun. 30, 2010 | Mar. 31, 2010 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Accumulated losses | $ 2,789.7 |  |  |  | $ 2,175.6 |  |  |  | $ 2,789.7 | $ 2,175.6 |
Noncontrolling interest in VIE | 580.2 |  |  |  | 607.8 |  |  |  | 580.2 | 607.8 |
Noncontrolling interest income (expense) related to VIE | 20.3 | (11.0) | 20.8 | 11.4 | 16.6 | 24.3 | 10.7 | 1.4 | 41.5 | 53.0 | 109.5
OneBeacon |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Noncontrolling interest in VIE | 287.2 |  |  |  | 314.9 |  |  |  | 287.2 | 314.9 |
Reciprocals | OneBeacon |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Number of reciprocals capitalized |  |  |  |  |  |  |  |  | 3 |  |
Houston General Insurance |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Total assets related to consolidated VIE's | 105.9 |  |  |  | 118.0 |  |  |  | 105.9 | 118.0 |
Total liabilities related to consolidated VIE's | 126.2 |  |  |  | 136.2 |  |  |  | 126.2 | 136.2 |
Houston General Insurance | OneBeacon |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Surplus notes | 23.7 |  |  |  |  |  |  |  | 23.7 |  |
Accumulated losses | 20.3 |  |  |  |  |  |  |  | 20.3 |  |
Accrued interest on surplus notes | 17.0 |  |  |  |  |  |  |  | 17.0 |  |
Prospector Offshore Fund |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Capital at risk, investment in the fund | 65.3 |  |  |  |  |  |  |  | 65.3 |  |
Total assets related to consolidated VIE's | 135.8 |  |  |  | 145.3 |  |  |  | 135.8 | 145.3 |
Total liabilities related to consolidated VIE's | 31.6 |  |  |  | 39.1 |  |  |  | 31.6 | 39.1 |
Noncontrolling interest in VIE | 38.9 |  |  |  | 40.6 |  |  |  | 38.9 | 40.6 |
Noncontrolling interest income (expense) related to VIE |  |  |  |  |  |  |  |  | 0.2 | (3.2) | (5.0)
Ownership interest in VIE (as a percent) |  |  |  |  |  |  |  |  | 62.65% |  |
Tuckerman Fund I |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Total assets related to consolidated VIE's | 17.6 |  |  |  | 19.4 |  |  |  | 17.6 | 19.4 |
Total liabilities related to consolidated VIE's | 9.9 |  |  |  | 12.3 |  |  |  | 9.9 | 12.3 |
Noncontrolling interest in VIE | 3.5 |  |  |  | 2.4 |  |  |  | 3.5 | 2.4 |
Noncontrolling interest income (expense) related to VIE |  |  |  |  |  |  |  |  | $ 2.2 | $ 1.0 | $ 0.7
Ownership interest in VIE (as a percent) |  |  |  |  |  |  |  |  | 94.00% |  |
Companies owned by the Tuckerman Fund I |  |  |  |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |  |  |  |
Number of small manufacturing companies owned by the Tuckerman Fund I from whom the entity received shares |  |  |  |  |  |  |  |  | 2 |  |

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- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.31) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 27 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 7 -Section 03 -Paragraph 20 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Name Accounting Research Bulletin (ARB) -Publisher AICPA -Number 51 -Paragraph 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition The portion of net Income or Loss attributable to the noncontrolling interest (if any) deducted in order to derive the portion attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6921930&loc=SL4573702-111684 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=6922042&loc=SL4591551-111686 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=6922042&loc=SL4591552-111686 + Details
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- Definition Financial instruments issued by insurance entities (surplus notes) that are includable in surplus for statutory accounting purposes as prescribed or permitted by state laws and regulations that are liabilities of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486086&loc=d3e24387-158525 + Details
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- Definition The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5710-111685 + Details
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- Definition The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5710-111685 + Details
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- Definition Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 5A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6970148&loc=SL6759159-111685 + Details
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- Definition Accrued interest on surplus notes issued by VIE. The interest is eliminated in consolidation with the primary beneficiary. + References No definition available. + Details
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- Definition Represents the number of manufacturing companies from whom the entity received the shares. + References No definition available. + Details
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