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Investment Securities (Investments Held on Deposit or as Collateral) (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014
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Investment securities |  |
Investments held in trusts | $ 104.8 | $ 103.4
Assets held by insurance regulators | 88.0 | 68.9
Surety Product Line [Member] | OneBeacon |  |
Investment securities |  |
Assets Held in Collateral | 137.7 | 81.0
Fixed maturity investments | White Mountains Life Re |  |
Investment securities |  |
Derivative Collateral Right to Reclaim | $ 0.0 | $ 9.5

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- Definition Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 320 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=28366721&loc=d3e22002-158495 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Cash and investments held in collateral. + References No definition available. + Details
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- Definition Investments Held In Trusts + References No definition available. + Details
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- Details
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- Details
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- Details
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