Commitments and Contingencies (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Clean-up costs accrued		$ 0.3	$ 6.8
Accrual for settlement of litigation				$ 2.3
Monthly lease payment	$ 0.4
Initial term of contract	10 years
Renewal term	1 year
Shell Pipeline Company L P
Loss Contingencies [Line Items]
Reimbursements related to costs and expenses for maintenance projects		$ 16.1	$ 3.0	$ 12.9