EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2009
Earnings Per Share, Basic [Line Items]
Net income	$ (7,511)	$ 20,374	$ 63,927	$ 24,509	$ 1,515	$ (10,177)	$ 74,217	$ 51,902	$ 101,299		$ 117,457		$ 27,242
Basic earnings per share
Weighted average shares of common stock outstanding-basic									41,359,000		41,364,000		42,119,000
Basic earnings per common share	$ (0.18)	$ 0.49	$ 1.55	$ 0.59	$ 0.04	$ (0.25)	$ 1.79	$ 1.25	$ 2.45		$ 2.84		$ 0.65
Diluted earnings per share
Incremental shares									209,000	[1]	266,000	[1]	346,000	[1]
Weighted average shares of common stock outstanding-diluted									41,568,000		41,630,000		42,465,000
Diluted earnings per common share	$ (0.18)	$ 0.49	$ 1.54	$ 0.59	$ 0.04	$ (0.25)	$ 1.78	$ 1.24	$ 2.44	[2]	$ 2.82	[2]	$ 0.64	[2]
Antidilutive securities excluded from computation of earnings per share, amount									0		0		0

[1] Incremental shares consist of stock options, stock awards and performance units.

[2] There were no anti-dilutive shares excluded from the calculation of diluted earnings per share for fiscal 2011, 2010 and 2009.