Stock Options and Employee Stock Purchase Plan - Schedule of Number of Shares Available for Grant (Detail) - shares	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Options, Outstanding Beginning Balance (in shares)	1,449,409	1,240,941
Options granted (in shares)	(243,881)	(317,619)
Options forfeited (in shares)	87,500	98,034
Options, Outstanding Ending Balance (in shares)	1,602,822	1,449,409
Qualified Employee Stock Option Plans [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Options, Outstanding Beginning Balance (in shares)	586,031	853,766
Options granted (in shares)	(233,381)	(307,119)
Options forfeited (in shares)	14,239	39,384
Options, Outstanding Ending Balance (in shares)	366,889	586,031
Director Stock Option Plans [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Options, Outstanding Beginning Balance (in shares)	17,000	19,500
Options granted (in shares)	(10,500)	(10,500)
Options forfeited (in shares)	0	8,000
Options, Outstanding Ending Balance (in shares)	6,500	17,000