Commitments and Contingencies (Details Textual) $ in Millions			6 Months Ended
	Jun. 01, 2017 bbl	Oct. 01, 2015 bbl	Jun. 30, 2017 USD ($)
Commitments and Contingencies (Textual) [Abstract]
Sites in various stages of follow-up			4
Sites with limited soil and ground water impact			2
Sites requiring additional investigation			2
Site contingency number of sites checked			6
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
Pipeline transportation capacity [Member]
Commitments and Contingencies (Textual) [Abstract]
Unrecorded Unconditional Purchase Obligation, Minimum Quantity Required | bbl		5,000
Term of unconditional purchase obligation		5 years
Unrecorded unconditional purchase obligation, annual amount			$ 9.4
Third-party pipeline [Member]
Commitments and Contingencies (Textual) [Abstract]
Unrecorded unconditional purchase obligation, annual amount			$ 11.9
Unrecorded Unconditional Purchase Obligation, Minimum Volume Per Day | bbl	5,000
Unrecorded Unconditional Purchase Obligation, Term	7 years
Crude Transportation [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked			5
SemCAMS [Member]
Commitments and Contingencies (Textual) [Abstract]
Asset retirement obligation liability			$ 20.4
Estimated cost to retire facilities			$ 126.4
SemGas [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked			1
Wapiti Sour Gas Plant [Member] [Member] | Capital Addition Purchase Commitments [Member]
Commitments and Contingencies (Textual) [Abstract]
Purchase Obligation, Due in Next Twelve Months			$ 80.0
Purchase Obligation, Due in Second Year			$ 155.0