Derivative Instruments and Hedging Activities (Details 1)	Sep. 30, 2011
Year 2011 [Member] | Collars [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	70.33
Ceiling price	101.74
Volume per Day	45,500
Year 2011 [Member] | Swap [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	79.18
Floor price	0
Ceiling price	0
Volume per Day	625
Year 2011 [Member] | Swap [Member] | Natural Gas Contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	6.27
Volume per Day	33,500
Year 2011 [Member] | Put [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	69.53
Ceiling price	0
Volume per Day	6,625
Year 2011 [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	52,750
Year 2012 [Member] | Collars [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	70.00
Ceiling price	106.86
Volume per Day	52,000
Year 2012 [Member] | Collars [Member] | Oil contracts [Member] | Q2 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	70.00
Ceiling price	119.44
Volume per Day	53,000
Year 2012 [Member] | Collars [Member] | Oil contracts [Member] | Q3 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	80.00
Ceiling price	128.57
Volume per Day	53,000
Year 2012 [Member] | Collars [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	80.00
Ceiling price	128.57
Volume per Day	53,000
Year 2012 [Member] | Swap [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	81.04
Floor price	0
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Swap [Member] | Oil contracts [Member] | Q2 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	81.04
Floor price	0
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Swap [Member] | Oil contracts [Member] | Q3 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	81.04
Floor price	0
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Swap [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	81.04
Floor price	0
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Swap [Member] | Natural Gas Contracts [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	6.53
Volume per Day	20,000
Year 2012 [Member] | Put [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	65.00
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Put [Member] | Oil contracts [Member] | Q2 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	65.00
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Put [Member] | Oil contracts [Member] | Q3 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	65.00
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Put [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	65.00
Ceiling price	0
Volume per Day	625
Year 2012 [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	53,250
Year 2012 [Member] | Oil contracts [Member] | Q2 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	54,250
Year 2012 [Member] | Oil contracts [Member] | Q3 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	54,250
Year 2012 [Member] | Oil contracts [Member] | Q4 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	54,250
Year 2013 [Member] | Collars [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Swap price	0
Floor price	70.00
Ceiling price	112.66
Volume per Day	16,000
Year 2013 [Member] | Oil contracts [Member] | Q1 [Member]
Commodity Derivative Contracts Not Classified as Hedging Instruments
Volume per Day	16,000