Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	$ 27,511	$ 18,114
Short-term Investments, Unrealized Gains		3
Short-term Investments, Unrealized Losses	(20)	(5)
Short-term Investments, Estimated Fair Value	27,491	18,112
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	17,342	15,166
Short-term Investments, Unrealized Losses	(19)	(5)
Short-term Investments, Estimated Fair Value	17,323	15,161
Government bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	10,169	2,948
Short-term Investments, Unrealized Gains		3
Short-term Investments, Unrealized Losses	(1)
Short-term Investments, Estimated Fair Value	$ 10,168	$ 2,951