Derivative Financial Instruments (Details) bbl in Thousands, BTU in Billions		May 03, 2018 BTU $ / EnergyContent $ / Barrels bbl	Mar. 31, 2018 BTU $ / EnergyContent $ / Barrels bbl
NYMEX Oil Swap Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,534
Derivative, Swap Type, Average Fixed Price | $ / Barrels			49.57
NYMEX Oil Swap Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,769
Derivative, Swap Type, Average Fixed Price | $ / Barrels			49.77
NYMEX Oil Swap Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,894
Derivative, Swap Type, Average Fixed Price | $ / Barrels			49.87
NYMEX Oil Swap Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,940
Derivative, Swap Type, Average Fixed Price | $ / Barrels			50.70
NYMEX Oil Swap Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			7,137
NYMEX Oil Collar Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,459
Derivative, Floor Price | $ / Barrels			50.00
Derivative, Ceiling Price | $ / Barrels			59.03
NYMEX Oil Collar Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,948
Derivative, Floor Price | $ / Barrels			50.00
Derivative, Ceiling Price | $ / Barrels			58.61
NYMEX Oil Collar Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			2,222
Derivative, Floor Price | $ / Barrels			50.00
Derivative, Ceiling Price | $ / Barrels			58.44
NYMEX Oil Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			5,908
Derivative, Floor Price | $ / Barrels			47.65
Derivative, Ceiling Price | $ / Barrels			59.19
NYMEX Oil Collar Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			11,537
Oil Basis Swap Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			2,392
Weighted-Average Contract Price | $ / Barrels	[1]		(1.03)
Oil Basis Swap Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			3,018
Weighted-Average Contract Price | $ / Barrels	[1]		(1.06)
Oil Basis Swap Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			3,327
Weighted-Average Contract Price | $ / Barrels	[1]		(1.08)
Oil Basis Swap Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			5,788
Weighted-Average Contract Price | $ / Barrels	[1]		(1.09)
Oil Basis Swap [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			14,525
Gas Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.31
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU			23,507
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU			(7,795)
Derivative, Swap Type, Weighted-Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.24
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU			15,712
Gas Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.29
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU			24,627
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU			(7,480)
Derivative, Swap Type, Weighted-Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.23
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU			17,147
Gas Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.29
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU			25,856
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU			(7,210)
Derivative, Swap Type, Weighted-Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.27
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU			18,646
Gas Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent			3.76
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU			41,394
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU			(24,415)
Derivative, Swap Type, Weighted-Average Fixed Price, Purchased Volumes | $ / EnergyContent			4.34
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU			16,979
Gas Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU	[2]		115,384
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU	[2]		(46,900)
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU	[2]		68,484
IF HSC [Member]
Derivative Financial Instruments
Index percent of natural gas fixed swaps			100.00%
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			915
Derivative, Swap Type, Average Fixed Price | $ / Barrels			10.87
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,033
Derivative, Swap Type, Average Fixed Price | $ / Barrels			10.99
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,146
Derivative, Swap Type, Average Fixed Price | $ / Barrels			11.18
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			3,533
Derivative, Swap Type, Average Fixed Price | $ / Barrels			12.31
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			539
Derivative, Swap Type, Average Fixed Price | $ / Barrels			11.13
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			7,166
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			554
Derivative, Swap Type, Average Fixed Price | $ / Barrels			24.94
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			610
Derivative, Swap Type, Average Fixed Price | $ / Barrels			24.27
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			671
Derivative, Swap Type, Average Fixed Price | $ / Barrels			24.39
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			1,503
Derivative, Swap Type, Average Fixed Price | $ / Barrels			27.83
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			3,338
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			84
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.69
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			93
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.70
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			102
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.70
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			154
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.64
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			433
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			66
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.07
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			70
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.07
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			76
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.07
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			117
Derivative, Swap Type, Average Fixed Price | $ / Barrels			35.70
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			329
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Second Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			175
Derivative, Swap Type, Average Fixed Price | $ / Barrels			50.99
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Third Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			202
Derivative, Swap Type, Average Fixed Price | $ / Barrels			51.13
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			208
Derivative, Swap Type, Average Fixed Price | $ / Barrels			50.99
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			197
Derivative, Swap Type, Average Fixed Price | $ / Barrels			50.93
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			0
Derivative, Swap Type, Average Fixed Price | $ / Barrels			0
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl			782
Subsequent Event [Member] | NYMEX Oil Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl		2,100
Subsequent Event [Member] | Oil Basis Swap Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl		500
Weighted-Average Contract Price | $ / Barrels		(3.80)
Subsequent Event [Member] | Oil Basis Swap Contract 2020 [Member]
Derivative Financial Instruments
Derivative, Nonmonetary Notional Amount, Volume | bbl		2,300
Subsequent Event [Member] | IF HSC Gas Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Floor Price | $ / EnergyContent		2.50
Derivative, Nonmonetary Notional Amount, Energy Measure, Sold Volumes | BTU		14,242
Minimum [Member] | Subsequent Event [Member] | NYMEX Oil Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Floor Price | $ / Barrels		50.00
Derivative, Ceiling Price | $ / Barrels		66.60
Minimum [Member] | Subsequent Event [Member] | Oil Basis Swap Contract 2020 [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / Barrels		(0.80)
Minimum [Member] | Subsequent Event [Member] | IF HSC Gas Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Ceiling Price | $ / EnergyContent		2.83
Maximum [Member] | Subsequent Event [Member] | NYMEX Oil Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Floor Price | $ / Barrels		55.00
Derivative, Ceiling Price | $ / Barrels		68.62
Maximum [Member] | Subsequent Event [Member] | Oil Basis Swap Contract 2020 [Member]
Derivative Financial Instruments
Weighted-Average Contract Price | $ / Barrels		(0.97)
Maximum [Member] | Subsequent Event [Member] | IF HSC Gas Collar Contract 2019 [Member]
Derivative Financial Instruments
Derivative, Ceiling Price | $ / EnergyContent		2.84

[1] Represents the price differential between WTI prices at Midland, Texas and WTI prices at Cushing, Oklahoma.

[2] Total net volumes of gas swaps are comprised 100% of IF HSC.