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Commitments and Contingencies (Legal Contingencies) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2007 | Dec. 31, 2015 | Dec. 31, 2014
Esurance [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Percentage of loss reserve development retained |  |  | 90.00%
OneBeacon | Pending Litigation [Member] | Tribune Company Litigation [Member] |  |  |
Legal Contingency [Abstract] |  |  |
Proceeds From Tribune Common Stock | $ 32.0 |  |
OneTitle [Member] |  |  |
Legal Contingency [Abstract] |  |  |
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest |  | 20.00% |
Surplus notes |  | $ 10.0 |
Sirius Group | Pending Litigation [Member] | Tribune Company Litigation [Member] |  |  |
Legal Contingency [Abstract] |  |  |
Proceeds From Tribune Common Stock | $ 6.1 |  |

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- Definition Percentage investment held by the managing member or general partner of the limited liability company (LLC) or limited partnership (LP). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 272 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055 + 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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