EARNINGS PER SHARE (Details) - 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
Basic, numerator:
NET INCOME	$ 4,989	$ 19,154	$ 19,967	$ 745	$ 14,543	$ 19,618	$ 17,208	$ (5,193)	$ 44,854	$ 46,177	$ 15,811
Effect of unvested restricted stock unit awards									(450)	(2,300)	(720)
Adjusted net income									$ 44,404	$ 43,877	$ 15,091
Basic, denominator:
Weighted-average shares	25,936,709	26,009,344	26,021,874	26,051,038	26,073,256	26,054,678	26,005,105	25,876,928	26,013,716	25,993,255	25,714,205
Earnings per common share (in dollars per share)	$ 0.19	$ 0.73	$ 0.76	$ 0.03	$ 0.53	$ 0.72	$ 0.63	$ (0.20)	$ 1.71	$ 1.69	$ 0.59
Diluted, numerator:
NET INCOME	$ 4,989	$ 19,154	$ 19,967	$ 745	$ 14,543	$ 19,618	$ 17,208	$ (5,193)	$ 44,854	$ 46,177	$ 15,811
Effect of unvested restricted stock unit awards									(443)	(2,300)	(720)
Adjusted net income									$ 44,411	$ 43,877	$ 15,091
Diluted, denominator:
Weighted-average shares	25,936,709	26,009,344	26,021,874	26,051,038	26,073,256	26,054,678	26,005,105	25,876,928	26,013,716	25,993,255	25,714,205
Effect of dilutive securities									516,411	357
Adjusted weighted-average shares and assumed conversions	26,415,839	26,508,482	26,593,451	26,588,518	26,073,256	26,054,678	26,005,105	25,876,928	26,530,127	25,993,612	25,714,205
Earnings per common share (in dollars per share)	$ 0.19	$ 0.72	$ 0.74	$ 0.03	$ 0.53	$ 0.72	$ 0.63	$ (0.20)	$ 1.67	$ 1.69	$ 0.59