SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 7) (USD $) In Thousands, except 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
Earnings per share
Net income (loss)									$ 48,828	$ 37,712	$ 37,656
Weighted average common shares, basic									41,892,000	41,762,000	41,612,000
Dilutive common stock options (treasury method) (in shares)										10,000	26,000
Shares used for dilutive computation									41,892,000	41,772,000	41,638,000
Net income per share - basic (in dollars per share)									$ 1.17	$ 0.90	$ 0.90
Diluted earnings per share (in dollars per share)	$ 0.12	$ 0.71	$ 0.31	$ 0.03	$ 0.04	$ 0.50	$ 0.29	$ 0.07	$ 1.17	$ 0.90	$ 0.90
Stock Appreciation Rights (SARs)
Stock-based awards included in earnings per share
Stock Appreciation Rights (SAR) outstanding	333,856				361,356				333,856	361,356	361,356