Earnings per Share - EPS Reconciliation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 16,300,000.0	$ 24,000,000.0	$ 57,900,000	$ 39,800,000
Less: Net income allocated to participating securities	(300,000)	(300,000)	(1,000,000)	(600,000)
Net income allocated to common shareholders	$ 16,000,000	$ 23,700,000	$ 56,900,000	$ 39,200,000
Weighted average number of common shares outstanding	18,781,401	18,597,165	18,731,203	18,524,846
Dilutive potential common shares outstanding:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	230,125	379,733	272,517	351,413
Diluted weighted-average shares	19,011,526	18,976,898	19,003,720	18,876,259