EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income (loss), as reported	$ (14,274)	$ 18,957	$ 249,691	$ 168,588
Basic earnings per share
Weighted average shares of common stock outstanding-basic (shares)	87,888,000	86,408,000	87,493,000	86,257,000
Basic (loss) earnings per common share (usd per share)	$ (0.16)	$ 0.22	$ 2.85	$ 1.95
Diluted earnings per share
Weighted average shares of common stock outstanding-basic (shares)	87,888,000	86,408,000	87,493,000	86,257,000
Incremental shares	0	859,000	391,000	831,000
Weighted average shares of common stock outstanding-diluted (shares)	87,888,000	87,267,000	87,884,000	87,088,000
Diluted (loss) earnings per common share (usd per share)	$ (0.16)	$ 0.22	$ 2.84	$ 1.94
Anti-dilutive shares excluded from the calculation of diluted earnings per share	402,000	0	0	0