DERIVATIVE INSTRUMENTS 3 (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets/liabilities	$ 40,544		$ 36,539
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	40,544		36,539
Gross amounts not offset in the balance sheet, Financial Instruments	(10,625)	[1]	(12,975)	[1]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	0		0
Net amount	29,919		23,564
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(55,950)		(29,231)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(55,950)		(29,231)
Gross amounts not offset in the balance sheet, Financial Instruments	10,625	[2]	12,975	[2]
Gross amounts not offset in the balance sheet, Cash Collateral Posted	13,952		6,347
Net amount	(31,373)		(9,909)
Interest Rate Contract [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized assets/liabilities	(8,106)		(13,462)
Gross amount offset in the balance sheet	0		0
Net amounts of assets/liabilities in balance sheet	(8,106)		(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	$ (8,106)		$ (13,462)

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

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