FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 item	Jun. 30, 2012 item	Dec. 31, 2012
Financial Assets and Liabilities Fair Value Measurement
Number of non-financial assets and liabilities impaired	0	0
Assets
Deferred compensation plan	$ 11,416		$ 10,608
Derivative Instruments	87,607		50,824
Total Assets	99,023		61,432
Liabilities
Deferred Compensation Plan	30,385		23,893
Derivative instruments			192
Total Liabilities	30,385		24,085
Transfer of Assets from Level 1 to Level 2	0	0
Transfer of Liabilities from Level 1 to Level 2	0	0
Transfer of Assets from Level 2 to Level 1	0	0
Transfer of Liabilities from Level 2 to Level 1	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Deferred compensation plan	11,416		10,608
Total Assets	11,416		10,608
Liabilities
Deferred Compensation Plan	30,385		23,893
Total Liabilities	30,385		23,893
Significant Other Observable Inputs (Level 2)
Assets
Derivative Instruments	3,729		9,473
Total Assets	3,729		9,473
Significant Unobservable Inputs (Level 3)
Assets
Derivative Instruments	83,878		41,351
Total Assets	83,878		41,351
Liabilities
Derivative instruments			192
Total Liabilities			$ 192