FAIR VALUE OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Changes in significant unobservable inputs [Roll forward]
Balance at beginning of period	$ (632)	$ (5,608)
Other changes in fair value from continuing and new contracts, net	10,015	(16,438)
Settlements	3,858	4,735
Balance at end of period	13,241	$ (17,311)
Fair Value, Measurements, Recurring
Assets
Available-for-Sale Securities	14,960		$ 14,810
Derivatives - Energy Related Assets	77,304		99,331
Total Assets	92,264		114,141
Liabilities
Derivatives - Energy Related Liabilities	76,518		112,405
Derivatives - Other	13,118		10,943
Total Liabilities	89,636		123,348
Fair Value, Measurements, Recurring | Level 1
Assets
Available-for-Sale Securities	2,945		2,925
Derivatives - Energy Related Assets	7,145		16,006
Total Assets	10,090		18,931
Liabilities
Derivatives - Energy Related Liabilities	31,858		42,170
Derivatives - Other	0		0
Total Liabilities	31,858		42,170
Fair Value, Measurements, Recurring | Level 2
Assets
Available-for-Sale Securities	12,015		11,885
Derivatives - Energy Related Assets	15,986		24,730
Total Assets	28,001		36,615
Liabilities
Derivatives - Energy Related Liabilities	3,728		11,008
Derivatives - Other	13,118		10,943
Total Liabilities	16,846		21,951
Fair Value, Measurements, Recurring | Level 3
Assets
Available-for-Sale Securities	0		0
Derivatives - Energy Related Assets	54,173		58,595
Total Assets	54,173		58,595
Liabilities
Derivatives - Energy Related Liabilities	40,932		59,227
Derivatives - Other	0		0
Total Liabilities	$ 40,932		$ 59,227