SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 7) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings per share:
Net income (loss)									$ 45,017	$ 56,738	$ 47,254
Weighted average common shares, basic (in shares)									47,865,000	47,791,000	46,384,000
Dilutive common stock equivalents (treasury method)									15,000	38,000	33,000
Shares used for dilutive calculation (in shares)									47,880,000	47,829,000	46,417,000
Earnings per share—basic (in dollars per share)									$ 0.94	$ 1.19	$ 1.02
Earnings per share—diluted (in dollars per share)	$ 0.18	$ 0.52	$ 0.21	$ 0.03	$ 0.24	$ 0.70	$ 0.36	$ (0.11)	$ 0.94	$ 1.19	$ 1.02
Stock Appreciation Rights (SARs)
Stock-based awards included in earnings per share
Stock Appreciation Rights (SAR) outstanding	64,500				186,356				64,500	186,356	283,856