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Investment Securities Investment Securities (OneBeacon Surplus Notes) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
RBC Score | 250.00% |
Total realized and unrealized gains (losses) | $ 11.6 | $ (226.8)
OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (29.1) | (49.5)
Current market rates on repayments | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | 5.1 | (15.1)
Regulatory Approval [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (15.6) | (24.2)
Liquidity Adjustment [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (18.6) | (10.2)
Fair Value [Member] | OneBeacon |  |
Surplus notes | 71.9 | 51.5
Par Value [Member] | OneBeacon |  |
Surplus notes | 101.0 | $ 101.0
Seller Priority Surplus Note [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (6.8) |
Seller Priority Surplus Note [Member] | Current market rates on repayments | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | 6.2 |
Seller Priority Surplus Note [Member] | Regulatory Approval [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (0.2) |
Seller Priority Surplus Note [Member] | Liquidity Adjustment [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (12.8) |
Seller Priority Surplus Note [Member] | Fair Value [Member] | OneBeacon |  |
Surplus notes | 51.1 |
Seller Priority Surplus Note [Member] | Par Value [Member] | OneBeacon |  |
Surplus notes | 57.9 |
Pari Passu Surplus Note [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (22.3) |
Pari Passu Surplus Note [Member] | Current market rates on repayments | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (1.1) |
Pari Passu Surplus Note [Member] | Regulatory Approval [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (15.4) |
Pari Passu Surplus Note [Member] | Liquidity Adjustment [Member] | OneBeacon |  |
Gain (loss) on sale of discontinued operations, net of tax | (5.8) |
Pari Passu Surplus Note [Member] | Fair Value [Member] | OneBeacon |  |
Surplus notes | 20.8 |
Pari Passu Surplus Note [Member] | Par Value [Member] | OneBeacon |  |
Surplus notes | $ 43.1 |

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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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