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Intangible Assets - Additional Information (Narrative) (Details) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2017	Oct. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Blue Waters
Finite-Lived Intangible Assets [Line Items]
Goodwill, acquired		$ 2.1
Trademarks
Finite-Lived Intangible Assets [Line Items]
Value of the asset			$ 1.9	$ 2.5	$ 2.9
Trademarks | Blue Waters
Finite-Lived Intangible Assets [Line Items]
Value of the asset			0.5
Aspen trademark
Finite-Lived Intangible Assets [Line Items]
Value of the asset			$ 1.4
Blue Waters
Finite-Lived Intangible Assets [Line Items]
Economic useful life			5 years
Insurance Licenses
Finite-Lived Intangible Assets [Line Items]
Value of the asset			$ 16.7	16.7	16.7
Renewal Rights
Finite-Lived Intangible Assets [Line Items]
Value of the asset			$ 0.0	$ 1.0	$ 1.4
Digital Re
Finite-Lived Intangible Assets [Line Items]
Goodwill, acquired	$ 1.8
Equity method investment, ownership percentage	49.00%

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- Definition

Finite And Indefinite Lived Intangible Assets By Major Class [Line Items]

+ References

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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- Definition

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

+ References

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