EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended
	Jan. 31, 2012	Apr. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jul. 22, 2009
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)			500,000	600,000	1,200,000
Basic earnings per share [Abstract]
Net income			$ 77,068	$ 73,142	$ 63,320
Income attributable to unvested stock-based compensation awards			(499)	(553)	(542)
Income available to common shareholders			76,569	72,589	62,778
Weighted-average common shares outstanding - basic (in shares)			39,192	35,767	32,951
Basic earnings per share (in dollars per share)			$ 1.95	$ 2.03	$ 1.91
Diluted earnings per share [Abstract]
Net income			77,068	73,142	63,320
Income attributable to unvested stock-based compensation awards			(499)	(553)	(542)
Income available to common shareholders			76,569	72,589	62,778
Weighted-average common shares outstanding (in shares)			39,192	35,767	32,951
Assumed exercise of stock options (in shares)			479	415	318
Weighted-average common shares outstanding - diluted (in shares)			39,671	36,182	33,269
Diluted earnings per share (in dollars per share)			$ 1.93	$ 2.01	$ 1.89
Common stock issuance	57,500		64,145	5,351	6,433
Common stock issuance (in shares)	2,130,000	3,350,000
Common stock issuance	$ 54,900		$ 54,917
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)			2,000,000	1,500,000		1,000,000