Supplemental Information (Components of Interest Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary of components of interest expense
Interest expense, net of capitalized interest	$ 26.0	$ 29.7	$ 48.6
Less: Interest income	1.0	1.4	1.1
Interest expense, net	$ 25.0	$ 28.3	$ 47.5