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Discontinued Operations - Interest Rate Cap (Details) $ in Millions	1 Months Ended		3 Months Ended			12 Months Ended
	Jul. 31, 2013 USD ($) shares	May. 31, 2007	Mar. 31, 2016 USD ($) Rating	Mar. 31, 2015 USD ($)	Sep. 30, 2013	Dec. 31, 2015 USD ($)
Preferred Stock [Member] | Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preferred Stock, Dividend Rate, Percentage		7.506%
Interest Rate Cap [Member] | Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
S and P Credit Ratings | Rating			21
Derivative collateral right to reclaim			$ 1.1
Years of interest rate cap					5 years
Derivative, Cap Interest Rate	8.30%
Derivative, Cost of Hedge	$ 9.9
Beginning of period			1.9	$ 4.1		$ 4.1
Realized and unrealized gains (losses)			(0.8)	(1.0)
End of period			1.1	$ 3.1		$ 1.9
Interest Rate Cap [Member] | Preferred Stock [Member] | Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of Stock, Number of Shares Issued in Transaction | shares	250,000,000.0
Sirius Group Ltd [Member] | Preferred Stock [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Term of LIBOR loan		3 months
Basis points		3.20%
Sirius Group Ltd [Member] | Interest Rate Cap [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Basis points	3.95%
Barclays [Member] | Standard & Poor's, A Rating [Member] | Interest Rate Cap [Member] | Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Derivative collateral right to reclaim			0.7
Nordea Bank Finland [Member] | Standard & Poor's, AA- Rating [Member] | Interest Rate Cap [Member] | Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Derivative collateral right to reclaim			$ 0.4

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