Schedule II, Valuation and Qualifying Accounts (Details) - Allowance for Bad Debts - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1		$ 5.6	$ 6.4	$ 6.4
Charged to costs and expenses		5.7	4.9	5.1
Charged to other accounts	[1]	1.5	1.0	1.2
Deductions from reserves	[2]	(7.5)	(6.7)	(6.3)
Balance at Dec. 31		$ 5.3	$ 5.6	$ 6.4

[1] Recovery of amounts previously written off.

[2] Deductions related primarily to bad debt write-offs