EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Earnings Per Share [Abstract]
Net income, as reported		$ 4,197	$ (7,460)	$ 60,903	$ 123,320	$ (24,420)	$ (14,274)	$ 172,971	$ 7,693	$ 180,960		$ 141,970		$ 114,809
Basic earnings per share
Weighted average shares of common stock outstanding-basic										85,186,000		84,198,000		83,316,000
Basic earnings per common share (in usd per share)		$ 0.05	$ (0.09)	$ 0.71	$ 1.46	$ (0.29)	$ (0.17)	$ 2.06	$ 0.09	$ 2.12		$ 1.69		$ 1.38
Diluted earnings per share
Weighted average shares of common stock outstanding-basic										85,186,000		84,198,000		83,316,000
Incremental shares	[1]									1,079,000		724,000		312,000
Weighted average shares of common stock outstanding-diluted										86,265,000		84,922,000		83,628,000
Diluted earnings per common share (in usd per share)		$ 0.05	$ (0.09)	$ 0.71	$ 1.44	$ (0.29)	$ (0.17)	$ 2.04	$ 0.09	$ 2.10	[2]	$ 1.67	[2]	$ 1.37	[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 2015, 2014 and 2013.