EARNINGS PER SHARE (Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic, numerator:
Net income	$ 40,776	$ 14,788	$ 51,963	$ 23,158
Effect of unvested restricted stock unit awards	(98)	(44)	(128)	(106)
Adjusted net income	$ 40,678	$ 14,744	$ 51,835	$ 23,052
Basic, denominator:
Weighted-average shares	25,697,509	25,671,535	25,670,435	25,699,306
Earnings per common share (in dollars per share)	$ 1.58	$ 0.57	$ 2.02	$ 0.90
Diluted, numerator:
Net income	$ 40,776	$ 14,788	$ 51,963	$ 23,158
Effect of unvested restricted stock unit awards	(94)	(43)	(124)	(104)
Adjusted net income	$ 40,682	$ 14,745	$ 51,839	$ 23,054
Diluted, denominator:
Weighted-average shares	25,697,509	25,671,535	25,670,435	25,699,306
Effect of dilutive securities	1,098,150	721,824	1,037,824	674,076
Adjusted weighted-average shares and assumed conversions	26,795,659	26,393,359	26,708,259	26,373,382
Earnings per common share (in dollars per share)	$ 1.52	$ 0.56	$ 1.94	$ 0.87