EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	200,000	800,000	200,000	700,000
Basic earnings per share [Abstract]
Net income	$ 17,191	$ 25,857	$ 43,448	$ 50,260
Income attributable to unvested stock-based compensation awards	(83)	(151)	(219)	(242)
Income available to common shareholders	$ 17,108	$ 25,706	$ 43,229	$ 50,018
Weighted-average common shares outstanding - basic (in shares)	48,525,000	44,021,000	46,913,000	43,942,000
Basic earnings per share (in dollars per share)	$ 0.35	$ 0.58	$ 0.92	$ 1.14
Diluted earnings per share [Abstract]
Net income	$ 17,191	$ 25,857	$ 43,448	$ 50,260
Income attributable to unvested stock-based compensation awards	(83)	(151)	(219)	(242)
Income available to common shareholders	$ 17,108	$ 25,706	$ 43,229	$ 50,018
Weighted-average common shares outstanding - basic (in shares)	48,525,000	44,021,000	46,913,000	43,942,000
Assumed exercise of stock options (in shares)	626,000	357,000	665,000	347,000
Weighted-average common shares outstanding - diluted (in shares)	49,151,000	44,378,000	47,578,000	44,289,000
Diluted earnings per share (in dollars per share)	$ 0.35	$ 0.58	$ 0.91	$ 1.13
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					2,200,000
Number of common shares repurchased (in shares)			0