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Fair Value of Financial Instruments (Details) - USD ($) $ in Millions | Mar. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt | $ 284.7 | $ 285.9
OneBeacon [Member] | 2012 OBH Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt | 273.2 | 273.2
OneBeacon [Member] | Book Value | 2012 OBH Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt | 273.2 | 273.2
OneBeacon [Member] | Estimate of Fair Value Measurement [Member] | 2012 OBH Senior Notes |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt Instrument, Fair Value Disclosure | 279.4 | 274.2
MediaAlpha [Member] | Book Value | MediaAlpha Bank Facility [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt | 11.5 | 12.7
MediaAlpha [Member] | Estimate of Fair Value Measurement [Member] | MediaAlpha Bank Facility [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions |  |
Debt Instrument, Fair Value Disclosure | $ 11.7 | $ 13.0

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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13476-108611 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: 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(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: 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(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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