DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Instruments (Detail) bbl in Thousands, MMBTU in Thousands, $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($) MMBTU Counterparty $ / MMBTU $ / bbl bbl
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative counterparties \| Counterparty	15
Put Options \| Crude Oil
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative remaining unamortized premium paid \| $	$ 12
Put Options \| October—December 2018 \| Crude Oil \| Dated Brent
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, volume (bbl) \| bbl	3,680
Derivative, weighted average strike price (USD per bbl) \| $ / bbl	56.00
Put Options \| October—December 2018 \| Crude Oil \| NYMEX WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, volume (bbl) \| bbl	2,760
Derivative, weighted average strike price (USD per bbl) \| $ / bbl	53.00
Collars \| October—December 2018 \| Crude Oil \| NYMEX WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, volume (bbl) \| bbl	1,702
Derivative, weighted average floor price (USD per bbl)	45.00
Derivative, weighted average ceiling price (USD per bbl)	57.00
Call Options \| Crude Oil
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative remaining unamortized premium paid \| $	$ 3
Call Options \| October—December 2018 \| Crude Oil \| NYMEX WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, volume (bbl) \| bbl	1,702
Derivative, weighted average strike price (USD per bbl) \| $ / bbl	60.03
Fixed-Price Swaps \| October—December 2018 \| Natural Gas \| NYMEX Henry Hub
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, weighted average fixed price (USD per MMBtu)	2.96
Derivative, nonmonetary notional amount, energy measure \| MMBTU	16,790
Finanical Basis Swaps \| October—December 2018 \| Crude Oil \| Midland-WTI/Cushing-WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	1,380
Weighted Average Price Differential	(9.23)
Finanical Basis Swaps \| October—December 2018 \| Natural Gas \| NYMEX Henry Hub
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	17,940
Weighted Average Price Differential	(0.53)
Finanical Basis Swaps \| January—September 2019 \| Crude Oil \| Midland-WTI/Cushing-WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	7,371
Weighted Average Price Differential	(8.60)
Finanical Basis Swaps \| October—December 2019 \| Crude Oil \| Midland-WTI/Cushing-WTI
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	1,380
Weighted Average Price Differential	(3.72)
Finanical Basis Swaps \| January—March 2019 \| Natural Gas \| NYMEX Henry Hub
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	1,350
Weighted Average Price Differential	(0.54)
Finanical Basis Swaps \| January—June 2019 \| Natural Gas \| NYMEX Henry Hub
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	32,580
Weighted Average Price Differential	(0.53)
Finanical Basis Swaps \| January—December 2019 \| Natural Gas \| NYMEX Henry Hub
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, nonmonetary notional amount, energy measure \| MMBTU	14,600
Weighted Average Price Differential	(0.45)

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- Definition

Derivative, Unamortized Premium

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- Definition

Derivative, Weighted Average Price Differential

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- Definition

The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

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The average floor rate on a group of price risk derivatives such as floors or collars. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

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The average strike price on the group of price risk option contracts such as put options or call options.

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Nominal energy measure used to calculate payments on a derivative instrument.

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Nominal volume used to calculate payments on a derivative instrument.

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Average fixed price related to the group of price risk swap derivatives.

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