Fair Value of Company's Short-term Investments, Contingemt Earn-Out Liability and Foreign Currency Forward Contracts (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	$ (9,940)	$ (7,713)
Total	(9,944)	17,488
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term Investments, Estimated Fair Value		17,791
Government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term Investments, Estimated Fair Value		7,680
Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward contract	(4)	(270)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total		25,471
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term Investments, Estimated Fair Value		17,791
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term Investments, Estimated Fair Value		7,680
Significant Other Observable (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	(4)	(270)
Significant Other Observable (Level 2) | Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward contract	(4)	(270)
Significant Unobservable (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	(9,940)	(7,713)
Total	$ (9,940)	$ (7,713)