Net Income (Loss) Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Employee and Directors Stock Options
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	313,028	316,776	313,787	341,776
Restricted Stock
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	66,688	97,535	67,694	97,685
Deferred Restricted Stock
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	29,050	16,550	29,050	16,550
Performance Shares
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	55,762	49,180	49,432	46,490