Derivative Financial Instruments (Details)	Mar. 31, 2015 bbl	Apr. 29, 2015 bbl
Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	12,100,000
Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	204,700,000
IF El Paso Permian [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	2.00%
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	79.00%
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%
IF Enable East [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps	11.00%
Index percent of natural gas collars	10.00%
Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,500,000
Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	9,600,000
Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	194,215,000
Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,462,000
Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	2,484,000
Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	10,478,000
Second Quarter Current Year [Member] | Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	1,639,000
Weighted-Average Contract Price	91.26
Second Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	15,985,000
Weighted-Average Contract Price	3.90
Second Quarter Current Year [Member] | Collar [Member] | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	709,000
Weighted-Average Floor Price	85.00
Weighted-Average Ceiling Price	94.06
Second Quarter Current Year [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	2,297,000
Weighted-Average Floor Price	4.00
Weighted-Average Ceiling Price	4.30
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	90.78
Third Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	14,950,000
Weighted-Average Contract Price	4.03
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	85.00
Weighted-Average Ceiling Price	91.25
Third Quarter Current Year [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	2,005,000
Weighted-Average Floor Price	4.00
Weighted-Average Ceiling Price	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	90.15
Fourth Quarter Current Year [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	13,570,000
Weighted-Average Contract Price	4.02
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	85.00
Weighted-Average Ceiling Price	92.19
Fourth Quarter Current Year [Member] | Collar [Member] | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	6,176,000
Weighted-Average Floor Price	3.97
Weighted-Average Ceiling Price	4.30
2016 [Member] | Swap | Crude oil
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	5,570,000
Weighted-Average Contract Price	88.01
2016 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	48,896,000
Weighted-Average Contract Price	4.12
2016 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	710,000
Weighted-Average Contract Price	9.12
2017 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	37,414,000
Weighted-Average Contract Price	4.16
2017 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	542,000
Weighted-Average Contract Price	10.13
2018 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	35,241,000
Weighted-Average Contract Price	4.21
2018 [Member] | Swap | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged	210,000
Weighted-Average Contract Price	10.74
2019 [Member] | Swap | Natural Gas [Member]
Derivative Financial Instruments
Portion of Gas Production Being Hedged	28,159,000
Weighted-Average Contract Price	4.28
Subsequent Event [Member] | Natural Gas Liquids
Derivative Financial Instruments
Portion of Future Oil and Gas Production Being Hedged		387,000
Maximum [Member] | Subsequent Event [Member] | Natural Gas Liquids
Derivative Financial Instruments
Derivative, Swap Type, Fixed Price		10.19
Minimum [Member] | Subsequent Event [Member] | Natural Gas Liquids
Derivative Financial Instruments
Derivative, Swap Type, Fixed Price		9.66
Line of Credit [Member] | Revolving Credit Facility [Member]
Derivative Financial Instruments
Percentage of Proved Property Secured for Credit Facility Borrowing	75.00%