Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash paid during the period for:
Interest (net of amount capitalized)	$ 163.7	$ 170.6	$ 170.6
Income taxes, net	0.5	0.7	0.3
Non-cash adjustments:
Accounts payable and PPE	$ 58.8	$ 93.4	$ 54.7