DERIVATIVE INSTRUMENTS 3 (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets/liabilities	$ 48,468		$ 36,539
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	48,468		36,539
Gross amounts not offset in the balance sheet, Financial Instruments	(10,162)	[1]	(12,975)	[1]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	0		0
Net amount	38,306		23,564
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(63,542)		(29,231)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(63,542)		(29,231)
Gross amounts not offset in the balance sheet, Financial Instruments	10,162	[2]	12,975	[2]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	24,078		6,347
Net amount	(29,302)		(9,909)
Interest Rate Contract [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(9,091)		(13,462)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(9,091)		(13,462)
Gross amounts not offset in the balance sheet, Financial Instruments	0		0
Gross amounts not offset in the balance sheet, Cash Collateral Posted	0		0
Net amount	$ (9,091)		$ (13,462)

[1] The balances at June 30, 2013 and December 31, 2012 were related to derivative liabilities which can be net settled against derivative assets.

[2] The balances at June 30, 2013 and December 31, 2012 were related to derivative assets which can be net settled against derivative liabilities.