DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Open Crude Oil and Natural Gas Derivative Instruments (Detail)	9 Months Ended
	Sep. 30, 2012
2012 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of collars derivative settled in 2012	31.00%
2013 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of collars derivative settled in 2013	58.00%
Fixed-Price Swaps [Member] | 2012 [Member] | Open Natural Gas Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
GJ	11,040,000
Weighted Average Fixed Price	6.61	[1]
Fixed-Price Swaps [Member] | 2012 [Member] | Open Natural Gas Derivative Positions [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	11,386,000
Weighted Average Fixed Price	6.24	[1]
Fixed-Price Swaps [Member] | 2012 [Member] | Open Crude Oil Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	941
Weighted Average Fixed Price	74.32	[2]
Fixed-Price Swaps [Member] | 2013 [Member] | Open Natural Gas Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	10,095,000
Weighted Average Fixed Price	6.74	[1]
Fixed-Price Swaps [Member] | 2013 [Member] | Open Crude Oil Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	1,972
Weighted Average Fixed Price	74.29	[2]
Fixed-Price Swaps [Member] | 2014 [Member] | Open Natural Gas Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	1,295,000
Weighted Average Fixed Price	6.72	[1]
Fixed-Price Swaps [Member] | 2014 [Member] | Open Crude Oil Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	76
Weighted Average Fixed Price	74.50	[2]
Collars [Member] | 2012 [Member] | Open Natural Gas Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
GJ	1,840,000
Collars Weighted Average Floor Price	6.50	[1]
Weighted Average Ceiling Price	7.27	[1]
Collars [Member] | 2012 [Member] | Open Natural Gas Derivative Positions [Member] | Currency Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	5,520,000
Collars Weighted Average Floor Price	5.54	[1]
Weighted Average Ceiling Price	7.30	[1]
Collars [Member] | 2012 [Member] | Open Crude Oil Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	2,808
Collars Weighted Average Floor Price	77.66	[2]
Weighted Average Ceiling Price	103.08	[2]
Collars [Member] | 2013 [Member] | Open Natural Gas Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	6,825,000
Collars Weighted Average Floor Price	5.35	[1]
Weighted Average Ceiling Price	6.67	[1]
Collars [Member] | 2013 [Member] | Open Crude Oil Derivative Positions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mbbls	5,701
Collars Weighted Average Floor Price	82.84	[2]
Weighted Average Ceiling Price	111.63	[2]

[1] U.S. natural gas prices represent a weighted average of several contracts entered into on a per-million British thermal units (MMBtu) basis and are settled primarily against NYMEX Henry Hub and various Inside FERC indices. The Canadian gas contracts are entered into on a per-gigajoule (GJ) basis and are settled against AECO Index. The Canadian natural gas prices represent a weighted average of AECO Index prices and are shown in Canadian dollars.

[2] Crude oil prices represent a weighted average of several contracts entered into on a per-barrel basis. Crude oil contracts are primarily settled against NYMEX WTI Cushing Index. Approximately 31 percent of 2012 collars and 58 percent of 2013 collars are settled against Dated Brent.