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Held for Sale and Discontinued Operations (Details) - USD ($) $ in Millions		12 Months Ended
	Aug. 20, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Discontinued Operations
Loss on sale of discontinued operations		$ (2.3)	$ 0.8	$ (17.2)
Corporate Aircraft
Discontinued Operations
Assets held for sale		1.7
Sirius Group
Discontinued Operations
Loss on sale of discontinued operations				(17.3)
Discontinued operations, liability			16.5
Connecticut | Held for Sale
Discontinued Operations
Proceeds from sale of property held-for-sale	$ 2.3
Realized gain losses on sales of other real estate		(0.1)
Assets held for sale		0.7	3.0
Swedish Tax Authority | Sirius Group
Discontinued Operations
Loss contingency due to foreign currency translations		(2.3)	0.8	$ (17.3)
Swedish Tax Authority | Sirius Group | Sirius Group
Discontinued Operations
Loss contingency accrual		18.7	$ 16.5
Loss contingency due to foreign currency translations		$ 2.2

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