Financial Instruments and Risk Management (WTI Open Contracts) (Details)	Sep. 30, 2016 bbl / d $ / bbl	Sep. 30, 2015 bbl / d $ / bbl
October - December 2016 [Member]
Oil and Gas Delivery Commitments and Contracts [Line Items]
Volumes (barrels per day) | bbl / d	25,000
Swap Prices | $ / bbl	50.67
January - December 2017 [Member]
Oil and Gas Delivery Commitments and Contracts [Line Items]
Volumes (barrels per day) | bbl / d	16,000
Swap Prices | $ / bbl	50.34
October - December 2015 [Member]
Oil and Gas Delivery Commitments and Contracts [Line Items]
Volumes (barrels per day) | bbl / d		15,000
Swap Prices | $ / bbl		63.30