EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Earnings Per Share [Abstract]
Net income (loss)	$ 29,155		$ (10,320)		$ 134,830		$ 101,572
Basic earnings per share
Weighted average shares of common stock outstanding-basic (in shares)	41,608		41,560		41,697		41,501
Basic earnings (loss) per common share	$ 0.70		$ (0.25)		$ 3.23		$ 2.45
Diluted earnings per share
Incremental shares	124	[1]	0	[1]	123	[1]	142	[1]
Weighted average shares of common stock outstanding-diluted (in shares)	41,732		41,560		41,820		41,643
Diluted earnings (loss) per common share	$ 0.70	[2]	$ (0.25)	[2]	$ 3.22	[2]	$ 2.44	[2]
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)	0		140		0		0

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

[2] Since there was a net loss for the three months ended June 30, 2012, incremental shares of 140 were not included in the computation of diluted loss per common share, as their effect would have been anti-dilutive. There were no anti-dilutive shares excluded from the calculation of diluted earnings per share for the three and nine months ended June 30, 2013 and the nine months ended June 30, 2012.