Fair Value Measurements - Summary of Financial Assets that are Measured at Fair Value and Indicates the Fair Value Hierarchy of the Valuation Inputs (Details) - USD ($)	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	$ 105,678,000	$ 113,099,000
Estimated fair value of cash and cash equivalents	69,230,000	101,437,000
Marketable Securities	36,448,000	11,662,000	$ 0
Money-Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	56,229,000	101,437,000
Estimated fair value of cash and cash equivalents	56,229,000	101,437,000
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	23,730,000	9,883,000
Estimated fair value of cash and cash equivalents	7,999,000
Marketable Securities	15,731,000	9,883,000
Corporate Debt Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value	25,719,000	1,779,000
Estimated fair value of cash and cash equivalents	5,002,000
Marketable Securities	$ 20,717,000	$ 1,779,000