Derivative Commodity Instruments (Reclassification) (Details) - Crude Oil - Production Period, Year One	12 Months Ended
	Dec. 31, 2015 MBbls $ / bbl
NYMEX Swaps
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	1,086
Average Contract Price | $ / bbl	63.80
WTI/WTI Basis Swaps
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	7,524	[1]
Average Contract Price | $ / bbl	(1.92)	[1]
WTS/WTI Basis Swaps
Derivatives, Fair Value [Line Items]
Total Hedged Volumes | MBbls	2,117	[2]
Average Contract Price | $ / bbl	(1.63)	[2]

[1] WTI - West Texas Intermediate/Midland, WTI - West Texas Intermediate/Cushing

[2] WTS - West Texas Sour/Midland, WTI - West Texas Intermediate/Cushing