Income Taxes Net Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 01, 2017	Dec. 31, 2016
Unrecognized Tax Benefits Recorded in Balance Sheet [Line Items]
Deferred income taxes	$ 15.5	$ 13.0
Other noncurrent liabilities	1.0	1.0
Net unrecognized tax benefits	16.5	14.0
Gross unrecognized tax benefits	$ 16.5	$ 14.0	$ 12.7	$ 12.5	$ 20.1