Investments - Summary of Investments by Type of Security (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Schedule Of Available For Sale Securities [Line Items]
Cost	$ 51,399	$ 70,314
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(911)	(1,413)
Short-term investments:	44,814	58,268
Long-term investments:	5,674	10,633
Fair Market Value	50,488	68,901
U.S. Treasury
Schedule Of Available For Sale Securities [Line Items]
Amortized cost, short-term	4,010	6,016
Amortized cost, long-term	3,420	3,431
Gross Unrealized Gains, short-term	0	0
Gross Unrealized Gains, long-term	0	0
Gross Unrealized Losses, short-term	(89)	(134)
Gross Unrealized Losses, long-term	(196)	(210)
Short-term investments:	3,921	5,882
Long-term investments:	3,224	3,221
Foreign government and agency securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost, short-term	2,854	2,865
Gross Unrealized Gains, short-term	0	0
Gross Unrealized Losses, short-term	(12)	(38)
Short-term investments:	2,842	2,827
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Amortized cost, short-term		18,245
Gross Unrealized Gains, short-term		0
Gross Unrealized Losses, short-term		(223)
Short-term investments:	15,429	18,022
Commercial paper | Short-Term Investments
Schedule Of Available For Sale Securities [Line Items]
Cost	15,680
Gross Unrealized Gains	0
Gross Unrealized Losses	(251)
Fair Market Value	15,429
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost, short-term	22,849	32,065
Amortized cost, long-term	2,586	7,692
Gross Unrealized Gains, short-term	0	0
Gross Unrealized Gains, long-term	0	0
Gross Unrealized Losses, short-term	(227)	(528)
Gross Unrealized Losses, long-term	(136)	(280)
Short-term investments:	22,622	31,537
Long-term investments:	$ 2,450	$ 7,412