Short-term Investments (Details) $ in Thousands	Sep. 30, 2018 USD ($)
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	7,702
Short-term Investments, Unrealized Losses	(22)
Short-term Investments, Estimated Fair Value	$ 7,680