Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost		$ 25,553
Short-term Investments, Unrealized Losses		(82)
Short-term Investments, Estimated Fair Value		25,471
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost		17,851
Short-term Investments, Unrealized Losses		(60)
Short-term Investments, Estimated Fair Value		17,791
Government bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	$ 747	7,702
Short-term Investments, Unrealized Gains	1
Short-term Investments, Unrealized Losses		(22)
Short-term Investments, Estimated Fair Value	$ 748	$ 7,680