FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Fair value of assets and liabilities on a recurring basis
Total assets	$ 49,126
Total liabilities	24,399
Fair Value, Measurements, Recurring | Using Significant Other Observable Inputs (Level 2)
Fair value of assets and liabilities on a recurring basis
Total assets	49,126	[1],[2]	100,043	[1],[2]
Total liabilities	24,399	[1],[2]	28,944	[1],[2]
Fair Value, Measurements, Recurring | Using Significant Other Observable Inputs (Level 2) | Commodity
Fair value of assets and liabilities on a recurring basis
Total assets	33,282	[1],[2]	79,487	[1],[2]
Total liabilities	24,399	[1],[2]	28,944	[1],[2]
Fair Value, Measurements, Recurring | Using Significant Other Observable Inputs (Level 2) | Interest rate
Fair value of assets and liabilities on a recurring basis
Total assets	15,844	[1],[2]	20,556	[1],[2]
Total liabilities	$ 0	[1],[2]	$ 0	[1],[2]

[1] The authoritative accounting guidance regarding fair value measurements for assets and liabilities measured at fair value establishes a three-tier fair value hierarchy, which prioritizes the inputs used to measure fair value. These tiers consist of: Level 1, defined as unadjusted quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for use when relevant observable inputs are not available. There were no transfers between levels of the fair value hierarchy during the three and nine months ended September 30, 2012. The Company’s policy is to recognize transfers between levels of the fair value hierarchy as of the beginning of the reporting period in which the event or change in circumstances caused the transfer.

[2] The Company’s derivative assets and liabilities include commodity and interest rate derivatives (see Note 8 for more information on these instruments). The Company utilizes present value techniques and option-pricing models for valuing its derivatives. Inputs to these valuation techniques include published forward prices, volatilities, and credit risk considerations, including the incorporation of published interest rates and credit spreads. All of the significant inputs are observable, either directly or indirectly; therefore, the Company’s derivative instruments are included within the Level 2 fair value hierarchy.