Allowance for Doubtful Accounts (Details) - Allowance for doubtful accounts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of components for doubtful accounts
Balance at Beginning of Period	$ 3.4	$ 3.8	$ 4.7
Additions	0.9	1.5	0.8
Deductions	(1.3)	(1.9)	(1.7)
Balance at End of Period	$ 3.0	$ 3.4	$ 3.8