NET INCOME PER SHARE (Basic and Diluted Net Income Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic net income per share:
Net income	$ 12,786	$ 13,211	$ 8,514	$ 6,693	$ 4,560	$ 11,243	$ 699	$ 11,487	$ 41,204	$ 27,989	$ 65,669
Weighted average common shares outstanding (in shares)									28,232	28,952	29,548
Basic net income per common share (in dollars per share)									$ 1.46	$ 0.97	$ 2.21
Diluted net income per share:
Net income	$ 12,786	$ 13,211	$ 8,514	$ 6,693	$ 4,560	$ 11,243	$ 699	$ 11,487	$ 41,204	$ 27,989	$ 65,669
Weighted average common shares outstanding (in shares)									28,232	28,952	29,548
Effect of dilutive securities:
Stock options and restricted stock (in shares)									284	543	601
Weighted average common shares for diluted earnings per share (in shares)									28,516	29,495	30,149
Diluted net income per common share (in dollars per share)									$ 1.44	$ 0.95	$ 2.17