Income Taxes - Movements in the Valuation Allowance (Details) - Valuation Allowance, Deferred Tax Asset - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ (21.4)	$ (17.3)
Increase (1)	(23.2)	(5.8)
Release	11.9	1.7
Ending balance	(32.7)	(21.4)
Previously Reported
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	(21.4)	(127.7)
Ending balance		(21.4)
Adjustment related to Separation
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 0.0	110.4
Ending balance		$ 0.0