Savings Plan - Additional Information (Detail) - USD ($)	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015
Postemployment Benefits [Abstract]
Defined savings plan contributions	$ 426,000	$ 402,000
Additional discretionary contributions	$ 0	$ 0

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration