Commitments and Contingencies (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Number_Of_Sites	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Commitments and Contingencies (Textual) [Abstract]
Estimated cost to retire facilities | $	$ 132,500
Asset Retirement Obligation Additional Estimated Costs Attributable To Third Party Owners Undiscounted | $	19,700
Asset Retirement Obligation, Revision of Estimate | $			$ (26,000)
Operating leases, rent expense | $	$ 15,400	$ 15,000	$ 15,500
Minimum [Member]
Commitments and Contingencies (Textual) [Abstract]
Notice required to cancel purchase agreements, days	30 days
Maximum [Member]
Commitments and Contingencies (Textual) [Abstract]
Notice required to cancel purchase agreements, days	120 days
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies (Textual) [Abstract]
Purchase Obligation, Due in Next Twelve Months | $	$ 206,000
Purchase Obligation, Due in Second Year | $	$ 53,000
Kansas sites [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked | Number_Of_Sites	6
Sites completing assessment | Number_Of_Sites	4
Number of Sites With Limited Soil and Groundwater Impact | Number_Of_Sites	2
Number of Sites Requiring Additional Investigation | Number_Of_Sites	2
Kansas sites [Member] | Crude Transportation [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked | Number_Of_Sites	5
Kansas sites [Member] | SemGas [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked | Number_Of_Sites	1