EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Earnings Per Share [Abstract]
Net income	$ (20,021)	$ 29,155	$ 45,469	$ 60,206	$ (8,693)	$ (10,320)	$ 54,535	$ 57,357	$ 114,809		$ 92,879		$ 101,299
Basic earnings per share
Basic earnings per common share (in usd per share)	$ (0.48)	$ 0.70	$ 1.09	$ 1.44	$ (0.21)	$ (0.25)	$ 1.31	$ 1.38	$ 2.76		$ 2.24		$ 2.45
Weighted average shares of common stock outstanding-basic									41,658		41,527		41,359
Diluted earnings per share
Incremental shares									156	[1]	105	[1]	209	[1]
Weighted average shares of common stock outstanding-diluted									41,814		41,632		41,568
Diluted earnings per common share (in usd per share)	$ (0.48)	$ 0.70	$ 1.08	$ 1.44	$ (0.21)	$ (0.25)	$ 1.31	$ 1.38	$ 2.75	[2]	$ 2.23	[2]	$ 2.44	[2]

[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 2013, 2012 and 2011.