Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Receivable
Valuation and Qualifying Accounts and Reserves
Balance at beginning of period	$ 0.7	$ 0.9	$ 0.3
Charged to costs and expenses	0.6		0.6
Deductions/Applications	0.2	0.2
Balance at end of period	1.1	0.7	0.9
Notes issued under par
Valuation and Qualifying Accounts and Reserves
Balance at beginning of period	62.2	63.8	45.1
Charged to costs and expenses	1.7	1.6	1.5
Additions			20.2
Balance at end of period	60.5	$ 62.2	$ 63.8
Valuation allowance
Valuation and Qualifying Accounts and Reserves
Charged to costs and expenses	619.6
Balance at end of period	$ 619.6