Investment In and Advances to Unconsolidated Affiliates - Balance Sheet of Equity Method Investments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets
Current assets	$ 64.5	$ 38.8
Property and equipment, net	234.6	198.0
Other assets, net	236.5	165.0
Total assets	535.6	401.8
Liabilities and Members' Equity
Current liabilities	100.3	77.5
Long-term debt	110.1	69.2
Other liabilities	0.1	0.1
Members' equity	325.1	255.0
Total liabilities and members' equity	$ 535.6	$ 401.8