EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	400,000	200,000
Basic earnings per share [Abstract]
Net income	$ 40,106	$ 26,257
Income attributable to unvested stock-based compensation awards	(141)	(138)
Income available to common shareholders	$ 39,965	$ 26,119
Weighted-average common shares outstanding - basic (in shares)	50,934,000	45,284,000
Basic earnings per share (in dollars per share)	$ 0.78	$ 0.58
Diluted earnings per share [Abstract]
Net income	$ 40,106	$ 26,257
Income attributable to unvested stock-based compensation awards	(141)	(138)
Income available to common shareholders	$ 39,965	$ 26,119
Weighted-average common shares outstanding - basic (in shares)	50,934,000	45,284,000
Assumed exercise of stock options (in shares)	563,000	703,000
Weighted-average common shares outstanding - diluted (in shares)	51,497,000	45,987,000
Diluted earnings per share (in dollars per share)	$ 0.78	$ 0.57
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)			2,500,000
Number of common shares repurchased (in shares)	0