Derivative Financial Instruments (Details)	Oct. 21, 2015 $ / Barrels bbl	Sep. 30, 2015 MMBTU $ / EnergyContent $ / Barrels bbl
Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		7,600,000
Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU		190,400,000
Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		13,700,000
Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		6,707,000
Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU		185,233,000
Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		869,000
Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged | MMBTU		5,157,000
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] | 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		3.61
Portion of Gas Production Being Hedged | MMBTU		80,186,000
2017 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / EnergyContent		4.09
Portion of Gas Production Being Hedged | MMBTU		37,527,000
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
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
IF NNG Ventura [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps		2.00%
Index percent of natural gas collars		5.00%
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps		95.00%
Index percent of natural gas collars		89.00%
IF NGPL TXOK [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps		1.00%
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps		2.00%
Index percent of natural gas collars		6.00%
OPIS Normal Butane Mont Belvieu Non-TET [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		595,000
OPIS Normal Butane Mont Belvieu Non-TET [Member] | Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		322,000
Weighted-Average Contract Price | $ / Barrels		24.90
OPIS Normal Butane Mont Belvieu Non-TET [Member] | 2016 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		273,000
Weighted-Average Contract Price | $ / Barrels		25.62
OPIS Normal Butane Mont Belvieu Non-TET [Member] | 2017 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Normal Butane Mont Belvieu Non-TET [Member] | 2018 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Normal Butane Mont Belvieu Non-TET [Member] | 2019 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Normal Butane Mont Belvieu Non-TET [Member] | 2020 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Ethane Purity Mont Belvieu [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		8,874,000
OPIS Ethane Purity Mont Belvieu [Member] | Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Ethane Purity Mont Belvieu [Member] | 2016 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		3,193,000
Weighted-Average Contract Price | $ / Barrels		8.47
OPIS Ethane Purity Mont Belvieu [Member] | 2017 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		2,271,000
Weighted-Average Contract Price | $ / Barrels		9.16
OPIS Ethane Purity Mont Belvieu [Member] | 2018 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		1,671,000
Weighted-Average Contract Price | $ / Barrels		10.65
OPIS Ethane Purity Mont Belvieu [Member] | 2019 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		1,200,000
Weighted-Average Contract Price | $ / Barrels		10.92
OPIS Ethane Purity Mont Belvieu [Member] | 2020 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		539,000
Weighted-Average Contract Price | $ / Barrels		11.13
OPIS Propane Mont Belvieu Non-TET [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		3,687,000
OPIS Propane Mont Belvieu Non-TET [Member] | Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		941,000
Weighted-Average Contract Price | $ / Barrels		19.60
OPIS Propane Mont Belvieu Non-TET [Member] | 2016 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		2,746,000
Weighted-Average Contract Price | $ / Barrels		19.09
OPIS Propane Mont Belvieu Non-TET [Member] | 2017 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Propane Mont Belvieu Non-TET [Member] | 2018 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Propane Mont Belvieu Non-TET [Member] | 2019 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Propane Mont Belvieu Non-TET [Member] | 2020 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Isobutane Mont Belvieu Non-TET [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		509,000
OPIS Isobutane Mont Belvieu Non-TET [Member] | Fourth Quarter Current Year [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		276,000
Weighted-Average Contract Price | $ / Barrels		25.30
OPIS Isobutane Mont Belvieu Non-TET [Member] | 2016 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		233,000
Weighted-Average Contract Price | $ / Barrels		25.87
OPIS Isobutane Mont Belvieu Non-TET [Member] | 2017 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Isobutane Mont Belvieu Non-TET [Member] | 2018 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Isobutane Mont Belvieu Non-TET [Member] | 2019 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
OPIS Isobutane Mont Belvieu Non-TET [Member] | 2020 [Member] | Swap | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		0
Weighted-Average Contract Price | $ / Barrels		0.00
Subsequent Event [Member] | Natural Gas Liquids [Member]
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	886,000
Weighted-Average Contract Price | $ / Barrels	20.16
Revolving Credit Facility [Member]
Derivative Financial Instruments
Percentage of Proved Property Secured for Credit Facility Borrowing		75.00%