EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	800,000	600,000	700,000	400,000
Basic earnings per share [Abstract]
Net income	$ 25,857	$ 23,840	$ 50,260	$ 46,137
Income attributable to unvested stock-based compensation awards	(151)	(99)	(242)	(177)
Income available to common shareholders	$ 25,706	$ 23,741	$ 50,018	$ 45,960
Weighted-average common shares outstanding - basic (in shares)	44,021,000	40,690,000	43,942,000	40,674,000
Basic earnings per share (in dollars per share)	$ 0.58	$ 0.58	$ 1.14	$ 1.13
Diluted earnings per share [Abstract]
Net income	$ 25,857	$ 23,840	$ 50,260	$ 46,137
Income attributable to unvested stock-based compensation awards	(151)	(99)	(242)	(177)
Income available to common shareholders	$ 25,706	$ 23,741	$ 50,018	$ 45,960
Weighted-average common shares outstanding - basic (in shares)	44,021,000	40,690,000	43,942,000	40,674,000
Assumed exercise of stock options (in shares)	357,000	404,000	347,000	405,000
Weighted-average common shares outstanding - diluted (in shares)	44,378,000	41,094,000	44,289,000	41,079,000
Diluted earnings per share (in dollars per share)	$ 0.58	$ 0.58	$ 1.13	$ 1.12
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