EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Jul. 22, 2009
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	300,000	600,000
Earnings per Share, Basic [Abstract]
Net income	$ 18,826	$ 16,160
Income attributable to unvested stock-based compensation awards	(104)	(131)
Income available to common shareholders	18,722	16,029
Weighted-average common shares outstanding - basic (in shares)	38,573,000	33,245,000
Basic earnings per share (in dollars per share)	$ 0.49	$ 0.48
Earnings Per Share, Diluted [Abstract]
Net income	18,826	16,160
Income attributable to unvested stock-based compensation awards	(104)	(131)
Income available to common shareholders	$ 18,722	$ 16,029
Weighted-average common shares outstanding (in shares)	38,573,000	33,245,000
Assumed exercise of stock options (in shares)	535,000	472,000
Weighted-average shares - diluted (in shares)	39,108,000	33,717,000
Diluted earnings per share (in dollars per share)	$ 0.48	$ 0.48
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)			1,500,000	1,000,000