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Summary of Significant Accounting Policies (Basis of Presentation) (Details) (USD $) In Millions, unless otherwise specified | 1 Months Ended | 12 Months Ended |  |  | 3 Months Ended |  |  |  |  |  |  | 1 Months Ended | 12 Months Ended
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Dec. 31, 2011 company | Dec. 31, 2013 state | Dec. 31, 2012 | Dec. 31, 2013 OneBeacon Ltd. | Dec. 31, 2012 OneBeacon Ltd. | Sep. 30, 2012 HG Global | Dec. 31, 2013 HG Global | Dec. 31, 2012 HG Global | Dec. 31, 2013 Redeemable preferred stocks HG Global | Dec. 31, 2012 Redeemable preferred stocks HG Global | Dec. 31, 2013 Common Stock HG Global | Dec. 31, 2012 Common Stock HG Global | Dec. 31, 2011 Tuckerman Fund I Common Stock | Dec. 31, 2011 Tuckerman Fund I Common Stock
Basis of Presentation |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions |  |  |  |  |  | $ 600.0 |  |  |  |  |  |  |  |
BAM Surplus notes |  |  |  |  |  |  | $ 503.0 | $ 503.0 |  |  |  |  |  |
Ownership interest (as a percent) |  |  |  | 75.20% | 75.20% |  | 97.30% |  | 97.30% | 97.30% | 88.70% | 88.70% |  |
Percentage of par value of policy reinsured |  |  | 15.00% |  |  |  | 15.00% |  |  |  |  |  |  |
Ownership interest in VIE (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 94.00% | 94.00%
Number of manufacturing companies | 2 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of states |  | 30 |  |  |  |  |  |  |  |  |  |  |  |
Workers compensation discount percent |  | 3.50% | 3.50% |  |  |  |  |  |  |  |  |  |  |
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners |  |  |  | 24.80% | 24.80% |  |  |  |  |  |  |  |  |

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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- Definition Total contributions made by each class of partners (i.e., general, limited and preferred partners). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770 + 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 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=28200181&loc=SL6759159-111685 + Details
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- Definition Percent discount applied to worker's compensation reserve liability to reduce the reserve to present value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Subparagraph b -Article 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6482852&loc=d3e14931-158439 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14754-158437 + 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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- Definition Represents the number of states in which insurance is directly written to customers. + References No definition available. + Details
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