EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income available to common shares	$ 34,525	$ 18,878	$ 105,973	$ 59,458
Denominator:
Weighted average common shares (Denominator for basis calculation) (in shares)	29,079,000	29,064,000	29,157,000	28,399,000
Weighted average effect of dilutive securities
Weighted average effect of dilutive securities (in shares)	377,000	504,000	446,000	525,000
Diluted weighted average common shares (Denominator for diluted calculation) (in shares)	29,456,000	29,568,000	29,603,000	28,924,000
Earnings per share:
Basic (in dollars per share)	$ 1.19	$ 0.65	$ 3.63	$ 2.09
Diluted (in dollars per share)	$ 1.17	$ 0.64	$ 3.58	$ 2.06
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options excluded from calculation of diluted earnings per share (in shares)	124,000	144,000	96,000	204,000