Summary of Combined Activity Under Equity Incentive Plans (Details) - $ / shares	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Number of Nonqualified Options, Beginning Balance	159,000	89,700	89,700
Granted, Number of Nonqualified Options Outstanding	51,300	69,300
Exercised, Number of Nonqualified Options Outstanding	(4,000)	0	0
Forfeited, Number of Nonqualified Options Outstanding	(4,500)
Vested, Number of Nonqualified Options Outstanding	0	0	0
Outstanding, Number of Nonqualified Options, Ending Balance	201,800	159,000	89,700
Options, Outstanding, Weighted Average Exercise Price per Share, Beginning Balance	$ 16.23	$ 17.27	$ 17.27
Granted, Weighted Average Exercise Price per Share	21.42	14.87
Exercised, Weighted Average Exercise Price per Share	8.78
Forfeited, Weighted Average Exercise Price per Share	26.48
Options, Outstanding, Weighted Average Exercise Price per Share, Ending Balance	17.47	16.23	17.27
Outstanding, Weighted Average Grant-date fair- value per Share, Beginning Balance	39.98	93.80	95.03
Granted, Weighted Average Grant-date fair- value per Share	21.12	14.84	19.13
Forfeited, Weighted Average Grant-date fair- value per Share	28.73	77.33	98.68
Vested, Weighted Average Grant-date fair- value per Share	22.02	90.73	95.02
Outstanding, Weighted Average Grant-date fair- value per Share, Ending Balance	$ 28.92	$ 39.98	$ 93.80
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options, Number of Restricted Stock Awards, Beginning Balance	273,650	142,500	189,000
Granted, Number of Restricted Stock Awards	109,500	182,400	3,000
Forfeited, Number of Restricted Stock Awards	(3,250)	(2,250)	(2,500)
Vested, Number of Restricted Stock Awards	(91,100)	(49,000)	(47,000)
Options, Number of Restricted Stock Awards, Ending Balance	288,800	273,650	142,500