EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income (loss), as reported	$ 18,957	$ (17,363)	$ 168,588	$ 106,272
Basic earnings per share
Weighted average shares of common stock outstanding-basic (shares)	86,408,000	85,960,000	86,257,000	85,823,000
Basic earnings per common share (usd per share)	$ 0.22	$ (0.20)	$ 1.95	$ 1.24
Diluted earnings per share
Weighted average shares of common stock outstanding-basic (shares)	86,408,000	85,960,000	86,257,000	85,823,000
Incremental shares	859,000	0	831,000	868,000
Weighted average shares of common stock outstanding-diluted (shares)	87,267,000	85,960,000	87,088,000	86,691,000
Diluted (loss) earnings per common share (usd per share)	$ 0.22	$ (0.20)	$ 1.94	$ 1.23
Anti-dilutive shares excluded from the calculation of diluted earnings per share	0	897,000	0	0