Related Party Transactions - Reimbursements from Our General Partner (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Related Party Transaction [Line Items]
Reimbursement of Zydeco directional drill	$ 4.1		$ 10.5
Refinery Gas Pipeline
Related Party Transaction [Line Items]
Reimbursement of Zydeco directional drill	0.6		0.6
Zydeco Pipeline Company LLC (“Zydeco”)
Related Party Transaction [Line Items]
Reimbursement of Zydeco directional drill	$ 3.5	$ 0.2	$ 9.9	$ 0.3