Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	$ 24,820	$ 27,511
Short-term Investments, Unrealized Losses	(81)	(20)
Short-term Investments, Estimated Fair Value	24,739	27,491
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	15,653	17,342
Short-term Investments, Unrealized Losses	(45)	(19)
Short-term Investments, Estimated Fair Value	15,608	17,323
Government bonds
Schedule Of Available For Sale Securities [Line Items]
Short-term Investments, Amortized Cost	9,167	10,169
Short-term Investments, Unrealized Losses	(36)	(1)
Short-term Investments, Estimated Fair Value	$ 9,131	$ 10,168