Derivative Financial Instruments (Details)	Sep. 30, 2014 bbl
Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	17,600,000
Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	164,100,000
Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,800,000
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	4.00%
Index percent of natural gas collars	4.00%
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	83.00%
Index percent of natural gas collars	80.00%
IF NGPL TXOK [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	2.00%
IF NNG Ventura [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	2.00%
Index percent of natural gas collars	8.00%
IF Enable East N/S [Member] [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	8.00%
Index percent of natural gas collars	8.00%
IF CIG [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	1.00%
OPIS Mont. Belvieu LDH Propane [Member]
Derivative Financial Instruments
Index percent of NGL fixed swaps	67.00%
OPIS Mont. Belvieu Non-LDH Natural Gasoline [Member]
Derivative Financial Instruments
Index percent of NGL fixed swaps	33.00%
Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	4,289,000
Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	13,002,000
Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	13,327,000
Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	151,059,000
Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,761,000
Fourth Quarter Current Year [Member] | Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	923,000
Weighted-Average Floor Price	85.00
Weighted-Average Ceiling Price	102.63
Fourth Quarter Current Year [Member] | Swap | Crude oil
Derivative Financial Instruments
Weighted-Average Contract Price	96.01
Portion of Future Oil and Gas Production Being Hedged	2,016,000
Fourth Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price	4.02
Portion of Gas Production Being Hedged	22,014,000
Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Weighted-Average Contract Price	61.69
Portion of Future Oil and Gas Production Being Hedged	980,000
2015 [Member] | Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	3,366,000
Weighted-Average Floor Price	85.00
Weighted-Average Ceiling Price	94.25
2015 [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Floor Price	3.98
Weighted-Average Ceiling Price	4.30
Portion of Gas Production Being Hedged	13,002,000
2015 [Member] | Swap | Crude oil
Derivative Financial Instruments
Weighted-Average Contract Price	91.14
Portion of Future Oil and Gas Production Being Hedged	5,741,000
2015 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price	4.04
Portion of Gas Production Being Hedged	57,943,000
2015 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Weighted-Average Contract Price	55.42
Portion of Gas Production Being Hedged	781,000
2016 [Member] | Swap | Crude oil
Derivative Financial Instruments
Weighted-Average Contract Price	88.01
Portion of Future Oil and Gas Production Being Hedged	5,570,000
2016 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price	4.17
Portion of Gas Production Being Hedged	37,472,000
2017 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price	4.21
Portion of Gas Production Being Hedged	23,430,000
2018 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price	4.31
Portion of Gas Production Being Hedged	10,200,000