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Stock-Based Compensation - Summary of Option Activity under Stock-Based Compensation Plan (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options granted	408,750
2009 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options granted	75,000
Number of Shares, Options exercised	(37,875)	(28,125)
Number of Shares, Options outstanding	483,750	446,625	474,750
Average Exercise Price Per Share, Options granted	$ 8.760
Average Exercise Price Per Share, Options exercised	5.126	$ 4.839
Average Exercise Price Per Share, Options outstanding	$ 5.684	$ 5.120	$ 5.103
1997 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options exercised	(30,000)
Number of Shares, Options expired	(11,250)
Number of Shares, Options outstanding	0	41,250	41,250
Average Exercise Price Per Share, Options exercised	$ 6.213
Average Exercise Price Per Share, Options expired	$ 6.213
Average Exercise Price Per Share, Options outstanding		$ 6.213	$ 6.213

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(4)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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