Debt (Schedule of Debt Issuance Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Issuance Costs [Roll Forward]
Debt issuance costs, beginning balance	$ 7.2	$ 10.3
Original issue discount, beginning balance	1.0	1.4
Amortization of debt issuance costs	(2.7)	(3.1)	$ (3.1)
Amortization of debt discount	(0.9)	(0.4)	(0.4)
Impacts from January 31, 2019 debt financing arrangement	20.2	0.0	4.7
Loss on debt extinguishment	(30.5)	0.0	(2.6)
Debt issuance costs, ending balance	9.3	7.2	10.3
Original issue discount, ending balance	0.0	$ 1.0	$ 1.4
Financing Arrangement, January 2019
Debt Issuance Costs [Roll Forward]
Impacts from January 31, 2019 debt financing arrangement	6.0
Impacts from January 31, 2019 debt financing arrangement	15.0
Financing Arrangement, February 2017
Debt Issuance Costs [Roll Forward]
Loss on debt extinguishment	(0.7)
Loss on debt extinguishment	(1.0)
Financing Arrangement, July 2019
Debt Issuance Costs [Roll Forward]
Loss on debt extinguishment	(0.5)
Loss on debt extinguishment	$ (14.1)