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Derivative Financial Instruments (Details) bbl in Thousands, BTU in Billions | Nov. 02, 2018 BTU $ / EnergyContent $ / Barrels bbl | Sep. 30, 2018 BTU $ / EnergyContent $ / Barrels bbl
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NYMEX Oil Swap Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 3,733
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 59.80
NYMEX Oil Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 2,491
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 65.68
NYMEX Oil Swap Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 8,118
NYMEX Oil Collar Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 10,055
Derivative, Floor Price | $ / Barrels |  |  | 50.59
Derivative, Ceiling Price | $ / Barrels |  |  | 63.62
NYMEX Oil Collar Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 1,165
Derivative, Floor Price | $ / Barrels |  |  | 55.00
Derivative, Ceiling Price | $ / Barrels |  |  | 66.47
NYMEX Oil Collar Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 13,442
Gas Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent |  |  | 3.27
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  |  | 28,204
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 |  |  | 20,994
Derivative, Swap Type, Average Fixed Price, Net of Purchased Volumes | $ / EnergyContent |  |  | 2.92
Gas Swaps Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent |  |  | 3.58
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  |  | 50,021
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 |  |  | 25,606
Derivative, Swap Type, Average Fixed Price, Net of Purchased Volumes | $ / EnergyContent |  |  | 2.85
Gas Swaps Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent |  |  | 2.82
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  |  | 2,942
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU |  |  | 0
Derivative, Swap Type, Weighted-Average Fixed Price, Purchased Volumes | $ / EnergyContent |  |  | 0.00
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU |  |  | 2,942
Derivative, Swap Type, Average Fixed Price, Net of Purchased Volumes | $ / EnergyContent |  |  | 2.82
Gas Swaps Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  |  | 81,167
Derivative, Nonmonetary Notional Amount, Energy Measure, Purchased Volumes | BTU |  |  | (31,625)
Derivative, Nonmonetary Notional Amount, Energy Measure, Net Volumes | BTU |  |  | 49,542
IF HSC Gas Collar Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Floor Price | $ / EnergyContent |  |  | 2.50
Derivative, Ceiling Price | $ / EnergyContent |  |  | 2.83
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  |  | 14,242
WTI Midland NYMEX WTI [Member] | Oil Basis Swap Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 3,327
Weighted-Average Contract Price | $ / Barrels | [1] |  | (1.08)
WTI Midland NYMEX WTI [Member] | Oil Basis Swap Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 11,217
Weighted-Average Contract Price | $ / Barrels | [1] |  | (3.36)
WTI Midland NYMEX WTI [Member] | Oil Basis Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 10,960
Weighted-Average Contract Price | $ / Barrels | [1] |  | (1.05)
WTI Midland NYMEX WTI [Member] | Oil Basis Swap Contract 2021 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 0
Weighted-Average Contract Price | $ / Barrels | [1] |  | 0.00
WTI Midland NYMEX WTI [Member] | Oil Basis Swap Contract 2022 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 0
Weighted-Average Contract Price | $ / Barrels | [1] |  | 0.00
WTI Midland NYMEX WTI [Member] | Oil Basis Swap [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 25,504
NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 0
Weighted-Average Contract Price | $ / Barrels | [2] |  | 0.00
NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 0
Weighted-Average Contract Price | $ / Barrels | [2] |  | 0.00
NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 1,840
Weighted-Average Contract Price | $ / Barrels | [2] |  | (8.01)
NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2021 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 3,650
Weighted-Average Contract Price | $ / Barrels | [2] |  | (7.86)
NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2022 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 3,650
Weighted-Average Contract Price | $ / Barrels | [2] |  | (7.78)
NYMEX WTI ICE Brent [Member] | Oil Basis Swap [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 9,140
OPIS Ethane Purity Mont Belvieu [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 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 |  |  | 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 |  |  | 5,218
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 1,980
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 28.89
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 0
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 0.00
OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 2,651
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 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 |  |  | 0
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 0.00
OPIS Normal Butane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 256
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 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 |  |  | 0
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 0.00
OPIS Isobutane Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 193
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 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 |  |  | 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 |  |  | 0
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  |  | 0.00
OPIS Natural Gasoline Mont Belvieu Non-TET [Member] | NGL Swaps Contracts [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  |  | 405
Subsequent Event [Member] | Gas Swaps Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU |  | 15,769 |
Subsequent Event [Member] | NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  | 900 |
Subsequent Event [Member] | OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract Fourth Quarter 2018 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  | 100 |
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  | 45.59 |
Subsequent Event [Member] | OPIS Propane Mont Belvieu Non-TET [Member] | NGL Swaps Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Nonmonetary Notional Amount, Volume |  | 400 |
Derivative, Swap Type, Average Fixed Price | $ / Barrels |  | 40.11 |
Minimum [Member] | Subsequent Event [Member] | Gas Swaps Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent |  | 2.80 |
Minimum [Member] | Subsequent Event [Member] | NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Weighted-Average Contract Price | $ / Barrels |  | (8.05) |
Maximum [Member] | Subsequent Event [Member] | Gas Swaps Contract 2019 [Member] |  |  |
Derivative Financial Instruments |  |  |
Derivative, Swap Type, Average Fixed Price | $ / EnergyContent |  | 3.42 |
Maximum [Member] | Subsequent Event [Member] | NYMEX WTI ICE Brent [Member] | Oil Basis Swap Contract 2020 [Member] |  |  |
Derivative Financial Instruments |  |  |
Weighted-Average Contract Price | $ / Barrels |  | (8.10) |
[1] | (1) Represents the price differential between WTI Midland (Midland, Texas) and NYMEX WTI (Cushing, Oklahoma).
[2] | (2) Represents the price differential between NYMEX WTI (Cushing, Oklahoma) and ICE Brent (North Sea).

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