Short-term Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	$ 27,122	$ 36,192
Short-term Investments, Unrealized Losses	(108)	(55)
Short-term Investments, Estimated Fair Value	27,014	36,137
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	18,345	22,829
Short-term Investments, Unrealized Losses	(86)	(31)
Short-term Investments, Estimated Fair Value	18,259	22,798
Government bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	8,777	13,363
Short-term Investments, Unrealized Losses	(22)	(24)
Short-term Investments, Estimated Fair Value	$ 8,755	$ 13,339

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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