Investments - Summary of Investments by Type of Security (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 18,693	$ 23,924
Gross Unrealized Gains	3	3
Gross Unrealized Losses	(8)	(6)
Fair Market Value	18,688	23,921
Corporate debt securities [Member] \| Short-term [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	10,479	23,924
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(1)	(6)
Fair Market Value	10,480	$ 23,921
Corporate debt securities [Member] \| Long-term [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	753
Gross Unrealized Losses	(3)
Fair Market Value	750
Government debt securities [Member] \| Short-term [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	4,458
Gross Unrealized Losses	(3)
Fair Market Value	4,455
Government debt securities [Member] \| Long-term [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	3,003
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Fair Market Value	$ 3,003

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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