Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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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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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.

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Number of Advertisers

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Represents the percentage of the total investment portfolio recorded at fair value based upon quoted market prices or other observable inputs.

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Percentage of par value of policy reinsured.

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Summary of Significant Accounting Policies (Basis of Presentation) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) publisher advertiser	Dec. 31, 2016 USD ($)	Sep. 28, 2017 $ / shares	Dec. 31, 2012 USD ($)
Basis of Presentation
Net unrealized foreign currency translation losses	$ (1.3)	$ (1.4)
Percentage of par value of policy reinsured	15.00%
Percentage of investments recorded at fair value	94.00%	94.00%
HG Global
Basis of Presentation
Surplus notes				$ 503.0
MediaAlpha
Basis of Presentation
Ownership interest (as a percent)	64.40%	60.00%
Number of advertisers \| advertiser	400
Number of publishers \| publisher	300
Preferred stocks \| HG Global
Basis of Presentation
Ownership interest (as a percent)	96.90%	96.90%
Common Stock \| HG Global
Basis of Presentation
Ownership interest (as a percent)	88.40%	88.40%
Intact Financial Corporation \| OneBeacon
Basis of Presentation
Sale of stock, price per share \| $ / shares			$ 18.10