EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	300,000	700,000	200,000	700,000
Basic earnings per share [Abstract]
Net income	$ 23,676	$ 21,122	$ 45,850	$ 41,363
Income attributable to unvested stock-based compensation awards	(123)	(114)	(221)	(189)
Income available to common shareholders	23,553	21,008	45,629	41,174
Weighted-average common shares outstanding - basic (in shares)	40,574,000	39,914,000	40,517,000	39,809,000
Basic earnings per share (in dollars per share)	$ 0.58	$ 0.53	$ 1.13	$ 1.03
Diluted earnings per share [Abstract]
Net income	23,676	21,122	45,850	41,363
Income attributable to unvested stock-based compensation awards	(123)	(114)	(221)	(189)
Income available to common shareholders	$ 23,553	$ 21,008	$ 45,629	$ 41,174
Weighted-average common shares outstanding - basic (in shares)	40,574,000	39,914,000	40,517,000	39,809,000
Assumed exercise of stock options (in shares)	484,000	427,000	497,000	445,000
Weighted-average common shares outstanding - diluted (in shares)	41,058,000	40,341,000	41,014,000	40,254,000
Diluted earnings per share (in dollars per share)	$ 0.57	$ 0.52	$ 1.11	$ 1.02
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