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Significant Transactions (Details) In Millions, unless otherwise specified | 3 Months Ended |  |  |  | 3 Months Ended |  | 12 Months Ended | 3 Months Ended |  | 1 Months Ended |  |  | 3 Months Ended | 2 Months Ended
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Mar. 31, 2014 USD ($) | Mar. 31, 2013 USD ($) | Dec. 31, 2013 USD ($) | Mar. 31, 2014 Star & Shield Insurance Exchange [Member] USD ($) | Jan. 31, 2013 Star & Shield Insurance Exchange [Member] USD ($) | Mar. 31, 2014 QuoteLab [Member] USD ($) | Mar. 14, 2014 QuoteLab [Member] USD ($) | Dec. 31, 2013 OneBeacon Essentia USD ($) | Mar. 31, 2013 WM Solutions [Member] Citation [Member] USD ($) | Mar. 31, 2013 WM Solutions [Member] American Fuji [Member] USD ($) | Mar. 31, 2014 WOBI [Member] | Feb. 19, 2014 WOBI [Member] USD ($) | Jan. 31, 2014 Star & Shield LLC [Member] USD ($) | Mar. 14, 2014 Common Class A [Member] QuoteLab [Member] | Feb. 19, 2014 Common Stock WOBI [Member] | Mar. 31, 2014 Noncontrolling interest Star & Shield Insurance Exchange [Member] USD ($) | Feb. 19, 2014 Israel, New Shekels Preferred Stock WOBI [Member] ILS | Feb. 19, 2014 Israel, New Shekels Common Stock WOBI [Member] ILS | Feb. 19, 2014 United States of America, Dollars Preferred Stock WOBI [Member] USD ($) | Feb. 19, 2014 United States of America, Dollars Common Stock WOBI [Member] USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest (as a percent) |  |  |  |  |  |  | 54.30% |  |  |  |  | 60.70% |  | 60.00% | 54.00% |  |  |  |  |
Payments to Acquire Businesses and Interest in Affiliates | $ 32.2 | $ 9.2 |  |  |  | $ 28.1 |  |  |  |  |  |  | $ 1.8 |  |  |  | 12.7 | 14.4 | $ 3.6 | $ 4.1
Premiums Written, Percentage of Total |  |  |  |  |  |  |  |  |  |  | 85.00% |  |  |  |  |  |  |  |  |
Number of lines of business |  |  |  |  |  |  |  |  |  |  | 4 |  |  |  |  |  |  |  |  |
Purchase of Surplus Notes |  |  |  |  | 12.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of gross profit |  |  |  |  |  |  | 62.50% |  |  |  |  |  |  |  |  |  |  |  |  |
Assets | 12,416.4 |  | 12,144.3 | 27.1 |  |  | 56.9 |  |  |  |  | 15.3 |  |  |  |  |  |  |  |
Intangible Assets, Net (Including Goodwill) |  |  |  |  |  |  | 43.7 |  |  |  |  |  |  |  |  |  |  |  |  |
Intangible Assets, Net |  |  |  |  |  |  |  |  |  |  |  | 15.0 |  |  |  |  |  |  |  |
Liabilities | 7,888.5 |  | 7,746.9 | 31.7 |  |  | 10.0 |  |  |  |  | 2.6 |  |  |  |  |  |  |  |
Net Income (Loss) Attributable to Noncontrolling Interest | 0.5 | 0.5 |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.7 |  |  |  |
Gain on sale of subsidiary | 0.7 | 23.0 |  |  |  |  |  | 23.0 | 0.7 | 6.9 |  |  |  |  |  |  |  |  |  |
Gain on sale of subsidiary, after tax |  |  |  |  |  |  |  | $ 15.0 |  |  |  |  |  |  |  |  |  |  |  |

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