DERIVATIVE INSTRUMENTS 2 (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Fair value Derivative Assets	$ 67,843	$ 99,273
Fair value Derivative Liabilities	118,337	140,402
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value Derivative Assets	67,843	99,273
Fair value Derivative Liabilities	118,337	140,402
Commodity Contract | Not Designated as Hedging Instrument | Derivatives-Energy Related-Current
Derivatives, Fair Value [Line Items]
Fair value Derivative Assets	52,441	85,368
Fair value Derivative Liabilities	81,779	109,744
Commodity Contract | Not Designated as Hedging Instrument | Derivatives-Energy Related-NonCurrent
Derivatives, Fair Value [Line Items]
Fair value Derivative Assets	15,402	13,905
Fair value Derivative Liabilities	24,522	19,926
Interest Rate Contract | Not Designated as Hedging Instrument | Derivatives-Other
Derivatives, Fair Value [Line Items]
Fair value Derivative Assets	0	0
Fair value Derivative Liabilities	$ 12,036	$ 10,732