Other Operating (Income) Expense (Parenthetical) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Other Operating Income Expense [Line Items]
(Gain) loss on sale or disposition of assets	[1]	$ (0.1)	$ 16.1
Venice Gathering System, L.L.C. [Member] | Not Qualify as Discontinued Operations [Member]
Other Operating Income Expense [Line Items]
(Gain) loss on sale or disposition of assets			$ 16.1

[1] Comprised primarily of a $16.1 million loss in the first quarter of 2017 due to the reduction in the carrying value of our ownership interest in VGS in connection with the April 4, 2017 sale.