EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income, as reported	$ (27,219)	$ 88,505	$ 89,361	$ (8,402)	$ 73,573	$ 86,248	$ 150,647	$ 151,419
Basic earnings per share
Weighted average shares of common stock outstanding-basic (in shares)	95,764,000			89,600,000			94,420,000	88,995,000
Basic (loss) earnings per common share (usd per share)	$ (0.28)			$ (0.09)			$ 1.60	$ 1.70
Diluted earnings per share
Weighted average shares of common stock outstanding-basic (in shares)	95,764,000			89,600,000			94,420,000	88,995,000
Other (in shares)	0			0			298,000	407,000
Weighted average shares of common stock outstanding-diluted (in shares)	95,764,000			89,600,000			94,718,000	89,402,000
Diluted (loss) earnings per common share (usd per share)	$ (0.28)			$ (0.09)			$ 1.59	$ 1.69
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)	310,000			409,000				0
Share-based Payment Arrangement
Diluted earnings per share
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)	251,780						95,817