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	$ 19.6	$ 19.6	$ 20.1
Charged to costs and expenses	16.4	14.3	14.1
Charged to other accounts	4.7	4.0	4.5
Deductions from reserves	(20.2)	(18.3)	(19.1)
Balance at Dec. 31	$ 20.5	$ 19.6	$ 19.6