Derivative Financial Instruments (Details) - Jun. 30, 2015	MMBTU $ / EnergyContent $ / Barrels bbl
Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	9,700,000
Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU	167,000,000
Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	9,500,000
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	5.00%
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	93.00%
Index percent of natural gas collars	88.00%
IF NGPL TXOK [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	1.00%
IF NNG Ventura [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	3.00%
Index percent of natural gas collars	7.00%
OPIS Ethane Purity Mont Belvieu [Member]
Derivative Financial Instruments
Index percent of natural gas liquid swaps	52.00%
OPIS Propane Mont Belvieu Non-TET [Member]
Derivative Financial Instruments
Index percent of natural gas liquid swaps	29.00%
OPIS Normal Butane Mont Belvieu Non-TET [Member]
Derivative Financial Instruments
Index percent of natural gas liquid swaps	10.00%
OPIS Isobutane Mont Belvieu Non-TET [Member]
Derivative Financial Instruments
Index percent of natural gas liquid swaps	9.00%
Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	7,961,000
Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU	159,862,000
Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	9,497,000
Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,775,000
Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU	7,162,000
Third Quarter Current Year [Member] | Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,254,000
Weighted-Average Contract Price | $ / Barrels	90.78
Third Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.03
Portion of Gas Production Being Hedged | MMBTU	12,835,000
Third Quarter Current Year [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,739,000
Weighted-Average Contract Price | $ / Barrels	21.61
Third Quarter Current Year [Member] | Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	906,000
Weighted-Average Floor Price | $ / Barrels	85.00
Weighted-Average Ceiling Price | $ / Barrels	91.25
Third Quarter Current Year [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU	2,005,000
Weighted-Average Floor Price | $ / EnergyContent	4.00
Weighted-Average Ceiling Price | $ / EnergyContent	4.30
Fourth Quarter Current Year [Member] | Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,137,000
Weighted-Average Contract Price | $ / Barrels	90.15
Fourth Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.01
Portion of Gas Production Being Hedged | MMBTU	12,499,000
Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,539,000
Weighted-Average Contract Price | $ / Barrels	21.73
Fourth Quarter Current Year [Member] | Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	869,000
Weighted-Average Floor Price | $ / Barrels	85.00
Weighted-Average Ceiling Price | $ / Barrels	92.19
Fourth Quarter Current Year [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU	5,157,000
Weighted-Average Floor Price | $ / EnergyContent	3.99
Weighted-Average Ceiling Price | $ / EnergyContent	4.29
2016 [Member] | Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	5,570,000
Weighted-Average Contract Price | $ / Barrels	88.01
2016 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.13
Portion of Gas Production Being Hedged | MMBTU	45,172,000
2016 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	2,017,000
Weighted-Average Contract Price | $ / Barrels	17.70
2017 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.19
Portion of Gas Production Being Hedged | MMBTU	34,335,000
2017 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	792,000
Weighted-Average Contract Price | $ / Barrels	9.98
2018 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.27
Portion of Gas Production Being Hedged | MMBTU	30,606,000
2018 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,671,000
Weighted-Average Contract Price | $ / Barrels	10.65
2019 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent	4.34
Portion of Gas Production Being Hedged | MMBTU	24,415,000
2019 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,200,000
Weighted-Average Contract Price | $ / Barrels	10.92
2020 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	539,000
Weighted-Average Contract Price | $ / Barrels	11.13