EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Basic Earnings (Loss) Per Share:
Net earnings	$ 13,494	$ 19,892	$ 5,264
Less: earnings allocated to unvested restricted stock	(326)	(678)	(122)
Net earnings allocated to common shares	13,168	19,214	5,142
Weighted-average basic shares and unvested restricted stock outstanding	37,391,100	37,420,300	37,284,000
Less: weighted-average unvested restricted stock outstanding (in shares)	(1,594,100)	(1,704,800)	(1,654,000)
Weighted-average basic shares outstanding	35,797,000	35,715,500	35,630,000
Basic earnings per share (in dollars per share)	$ 0.37	$ 0.54	$ 0.14
Diluted Earnings Per Share:
Net earnings allocated to common shares	$ 13,168	$ 19,214	$ 5,142
Weighted-average basic shares outstanding	35,797,000	35,715,500	35,630,000
Diluted earnings per share (in dollars per share)	$ 0.37	$ 0.54	$ 0.14