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Held for Sale and Discontinued Operations - (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Discontinued Operations [Line Items}
Net gain from sale of discontinued operations, net of tax	$ (1.0)	$ 0.0	$ (0.1)	$ 0.7
Connecticut \| Discontinued Operations, Held-for-sale
Discontinued Operations [Line Items}
Assets held for sale	3.0		3.0		$ 3.0
Sirius Group \| Swedish Tax Authority \| Sirius Group
Discontinued Operations [Line Items}
Contingent liability	16.5		$ 16.5		$ 16.5
Change in contingent liability	$ (1.0)