SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Provision for Uncollectible Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, at beginning of year	$ 6.0	$ 5.6	$ 6.0
Additions Charged to Expenses	5.9	6.9	8.1
Additions Charged to Other Accounts	0.0	0.0	0.0
Deductions from Reserves, Net	6.8	6.5	8.5
Balance, at end of period	5.1	6.0	5.6
Reserve for Impaired Notes Receivable
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, at beginning of year	0.6	0.2	0.0
Additions Charged to Expenses	0.4	0.4	0.2
Additions Charged to Other Accounts	0.0	0.0	0.0
Deductions from Reserves, Net	0.0	0.0	0.0
Balance, at end of period	$ 1.0	$ 0.6	$ 0.2