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Commitments and Contingencies (Legal Contingencies) (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2007 | Dec. 31, 2016
OneBeacon | Pending Litigation [Member] | Tribune Company Litigation [Member] |  |
Loss Contingencies [Line Items] |  |
Proceeds From Tribune Common Stock | $ 32.0 |
OneTitle [Member] |  |
Loss Contingencies [Line Items] |  |
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] |  |
Loss Contingencies [Line Items] |  |
Proceeds From Tribune Common Stock | $ 6.1 |

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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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