Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Accrued capital expenditures	$ 24.5	$ 33.9	$ 28.2	$ 50.7
Capital Lease Obligations Incurred	$ 201.2	$ 0.0