Fair Value Measurements - Summary of Financial Assets that are Measured at Fair Value and Indicates the Fair Value Hierarchy of the Valuation Inputs (Parenthetical) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, cost	$ 23,730	$ 9,883
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities, cost	$ 25,734	$ 1,780