EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	300,000	300,000	200,000	500,000
Basic earnings per share [Abstract]
Net income	$ 22,371	$ 21,989	$ 68,220	$ 63,352
Income attributable to unvested stock-based compensation awards	(115)	(121)	(337)	(315)
Income available to common shareholders	22,256	21,868	67,883	63,037
Weighted-average common shares outstanding - basic (in shares)	40,596,000	40,121,000	40,543,000	39,914,000
Basic earnings per share (in dollars per share)	$ 0.55	$ 0.55	$ 1.67	$ 1.58
Diluted earnings per share [Abstract]
Net income	22,371	21,989	68,220	63,352
Income attributable to unvested stock-based compensation awards	(115)	(121)	(337)	(315)
Income available to common shareholders	$ 22,256	$ 21,868	$ 67,883	$ 63,037
Weighted-average common shares outstanding - basic (in shares)	40,596,000	40,121,000	40,543,000	39,914,000
Assumed exercise of stock options (in shares)	453,000	506,000	482,000	474,000
Weighted-average common shares outstanding - diluted (in shares)	41,049,000	40,627,000	41,025,000	40,388,000
Diluted earnings per share (in dollars per share)	$ 0.54	$ 0.54	$ 1.65	$ 1.56
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					2,000,000
Number of common shares repurchased (in shares)			0		0