EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Jul. 22, 2009
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)			500,000	600,000
Earnings per Share, Basic [Abstract]
Net income	$ 18,367	$ 20,008	$ 58,264	$ 54,154
Income attributable to unvested stock-based compensation awards	(125)	(147)	(372)	(414)
Income available to common shareholders	18,242	19,861	57,892	53,740
Weighted-average common shares outstanding - basic (in shares)	39,384	36,679	39,095	35,436
Basic earnings per share (in dollars per share)	$ 0.46	$ 0.54	$ 1.48	$ 1.52
Earnings Per Share, Diluted [Abstract]
Net income	18,367	20,008	58,264	54,154
Income attributable to unvested stock-based compensation awards	(125)	(147)	(372)	(414)
Income available to common shareholders	$ 18,242	$ 19,861	$ 57,892	$ 53,740
Weighted-average common shares outstanding (in shares)	39,384	36,679	39,095	35,436
Assumed exercise of stock options (in shares)	486	362	496	403
Weighted-average shares - diluted (in shares)	39,870	37,041	39,591	35,839
Diluted earnings per share (in dollars per share)	$ 0.46	$ 0.54	$ 1.46	$ 1.50
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					1,500,000	1,000,000