Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income available to common shares	$ 31,530	$ 38,549
Denominator:
Weighted average common shares (in shares)	29,123,000	29,137,000
Weighted average effect of dilutive securities
Weighted average effect of dilutive securities (in shares)	475,000	557,000
Diluted weighted average common shares (in shares)	29,598,000	29,694,000
Earnings per share:
Basic (in dollars per share)	$ 1.08	$ 1.32
Diluted (in dollars per share)	$ 1.07	$ 1.30
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding stock options (in shares)	15,000	36,000