Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 9.6	[1]	$ 8.9	[2]	$ 19.1	[1],[3]	$ 18.0	[2],[4]

[1] The 2017 financial information reflects adjustments for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations from January 1, 2017 through May 9, 2017.

[2] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.

[3] The 2017 financial information reflects adjustments for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations from January 1, 2017 through May 9, 2017.

[4] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.