DERIVATIVE INSTRUMENTS (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative contracts not designated as hedging instruments and the location of gain or (loss) recognized in income statement
Realized gains on commodity derivatives	$ (31,067,000)	$ (2,271,000)	$ (52,395,000)	$ (12,839,000)
Unrealized (gains) losses on commodity derivatives	(2,126,000)	(30,586,000)	(8,572,000)	15,772,000
Realized gains on interest rate derivatives	(2,837,000)	(2,872,000)	(5,721,000)	(5,842,000)
Unrealized losses (gains) on interest rate derivatives	2,015,000	(5,188,000)	3,149,000	(1,762,000)
Realized and unrealized gains on derivative instruments, net	(34,015,000)	(40,917,000)	(63,539,000)	(4,671,000)
Credit Risk
Derivative, Net Asset Position, Aggregate Fair Value	79,700,000		79,700,000
Number of counterparties to whom derivative liabilities are owed	1		1
Derivative, Net Liability Position, Aggregate Fair Value	3,200,000		3,200,000
Maximum exposure of entity to risk, if the netting provisions of the ISDA Master Agreements did not exist	100,900,000		100,900,000
Maximum exposure of counterparties to risk, if the netting provisions of the ISDA Master Agreements did not exist	$ 24,400,000		$ 24,400,000