EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 29, 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 Earnings (Loss) Per Share:
Net earnings (loss)	$ 19,892	$ 16,088	$ 15,557	$ 5,264	$ 13,883	$ 13,304	$ 12,841	$ 10,676	$ 56,801	$ 50,704	$ (62,016)
Less: earnings allocated to unvested restricted stock									(1,845)	(2,072)	(31)
Net earnings (loss) allocated to common shares									54,956	48,632	(62,047)
Weighted-average basic shares and unvested restricted stock outstanding									37,369,500	37,141,500	36,438,700
Less: weighted-average unvested restricted stock outstanding (in shares)									(1,685,400)	(1,650,700)	(1,330,600)
Weighted-average basic shares outstanding									35,684,100	35,490,800	35,108,100
Basic earnings (loss) per share (in dollars per share)	$ 0.54	$ 0.43	$ 0.42	$ 0.14	$ 0.38	$ 0.36	$ 0.35	$ 0.29	$ 1.54	$ 1.37	$ (1.77)
Diluted Earnings (Loss) Per Share:
Net earnings (loss) allocated to common shares									$ 54,956	$ 48,632	$ (62,047)
Weighted-average basic shares outstanding									35,684,100	35,490,800	35,108,100
Diluted earnings (loss) per share (in dollars per share)	$ 0.54	$ 0.43	$ 0.42	$ 0.14	$ 0.38	$ 0.36	$ 0.35	$ 0.29	$ 1.54	$ 1.37	$ (1.77)