Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at end of year	$ 4.3
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	6.7	$ 6.3	$ 7.9
Additions charged to cost and expenses	3.9	2.4	2.8
Write-offs	(5.6)	(2.7)	(4.9)
Recoveries	0.9	0.9	1.1
Other	0.0	(0.2)	(0.6)
Balance at end of year	$ 5.9	$ 6.7	$ 6.3