EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Earnings Per Share [Abstract]
Net income, as reported	$ (24,420)	$ (14,274)	$ 172,971	$ 7,693	$ (20,021)	$ 29,155	$ 45,469	$ 60,206	$ 141,970		$ 114,809		$ 92,879
Basic earnings per share
Weighted average shares of common stock outstanding-basic									42,099,000		41,658,000		41,527,000
Basic earnings per common share (in usd per share)	$ (0.58)	$ (0.34)	$ 4.11	$ 0.18	$ (0.48)	$ 0.70	$ 1.09	$ 1.44	$ 3.37		$ 2.76		$ 2.24
Diluted earnings per share
Weighted average shares of common stock outstanding-basic									42,099,000		41,658,000		41,527,000
Incremental shares									362,000	[1]	156,000	[1]	105,000	[1]
Weighted average shares of common stock outstanding-diluted									42,461,000		41,814,000		41,632,000
Diluted earnings per common share (in usd per share)	$ (0.58)	$ (0.34)	$ 4.07	$ 0.18	$ (0.48)	$ 0.70	$ 1.08	$ 1.44	$ 3.34	[2]	$ 2.75	[2]	$ 2.23	[2]
Anti-dilutive securities excluded from the calculation of diluted earnings per share (in shares)									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 2014, 2013 and 2012.