Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Sep. 30, 2016
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	$ 28,932	$ 27,511
Short-term Investments, Unrealized Losses	(70)	(20)
Short-term Investments, Estimated Fair Value	28,862	27,491
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	18,767	17,342
Short-term Investments, Unrealized Losses	(44)	(19)
Short-term Investments, Estimated Fair Value	18,723	17,323
Government bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	10,165	10,169
Short-term Investments, Unrealized Losses	(26)	(1)
Short-term Investments, Estimated Fair Value	$ 10,139	$ 10,168