Schedule II, Valuation and Qualifying Accounts (Details) - Allowance for Bad Debts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1	$ 4.9	$ 4.9	$ 5.1
Charged to costs and expenses	4.2	4.1	3.7
Charged to other accounts	1.0	0.9	1.1
Deductions from reserves	(4.5)	(5.0)	(5.0)
Balance at Dec. 31	$ 5.6	$ 4.9	$ 4.9