EARNINGS (LOSS) PER COMMON 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
Net (Loss) Income
Basic (loss) earnings per share	$ (4,349)	$ 99,505	$ (23,541)	$ 261,023
Restricted stock and performance units	0	0	0	0
Diluted (loss) earnings per share	$ (4,349)	$ 99,505	$ (23,541)	$ 261,023
Shares
Basic earnings per share (in shares)	80,542,000	64,795,000	74,515,000	64,750,000
Restricted stock and performance units (in shares)	0	52,000	0	102,000
Diluted (loss) earnings per share (in shares)	80,542,000	64,847,000	74,515,000	64,852,000
Per Share Amount
Basic earnings per share (in dollars per share)	$ (0.05)	$ 1.54	$ (0.32)	$ 4.03
Restricted stock and performance units (in dollars per share)	0.00	(0.01)	0.00	(0.01)
Diluted (loss) earnings per share (in dollars per share)	$ (0.05)	$ 1.53	$ (0.32)	$ 4.02
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options, excluded in the calculation of earnings per share (in shares)	2,811,956	2,377,436	3,046,982	2,070,774
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options, excluded in the calculation of earnings per share (in shares)	716,000		481,000