NET INCOME PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
NET INCOME PER COMMON SHARE
Net income applicable to common stock	$ 63,692	$ 54,477	$ 20,896
Shares of common stock outstanding used to compute basic per common share amounts	34,282,591	33,544,813	32,238,401
Effect of dilutive restricted stock and options (in shares)	550,239	675,443	649,904
Shares used to compute diluted per common share amounts	34,832,830	34,220,256	32,888,305
Basic income per share applicable to common stock (in dollars per share)	$ 1.86	$ 1.62	$ 0.65
Diluted income per share applicable to common stock (in dollars per share)	$ 1.83	$ 1.59	$ 0.64