Net Income (Loss) Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Employee and Directors Stock Options
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	316,776	299,667	341,776	322,417
Restricted Stock
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	97,535	107,210	97,685	108,498
Deferred Restricted Stock
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	16,550		16,550
Performance Shares
Antidilutive securities
Number of shares excluded as their effect would be anti-dilutive	49,180	9,500	46,490	14,250