Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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Amount of Net Income (Loss) attributable to noncontrolling interest.

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The cash outflow associated with the acquisition of a controlling interest in another entity or an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, joint venture or equity method investment).

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Gain (Loss) on Disposition of Stock in Subsidiary, After Tax

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Number of lines of business

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Percentage of gross profit

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Premiums Written, Percentage of Total

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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
	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