Stock-Based Compensation - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Oct. 01, 2023	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, share reserve for issuance (in shares)		2,282,102		2,282,102
Granted (in shares)				0	0
Number of options outstanding (in shares)		1,525,717		1,525,717		1,978,516
Stock-based compensation expense		$ 15,081,000	$ 16,588,000	$ 29,257,000	$ 34,273,000
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		5,933,743		5,933,743		4,913,312
Stock-based compensation expense		$ 15,100,000	16,000,000.0	$ 29,200,000	32,200,000
Unrecognized pre-tax compensation expense		97,900,000		$ 97,900,000
Weighted average period to recognize pre-tax compensation expense				1 year 9 months 18 days
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised		3,700,000	2,500,000	$ 4,600,000	3,100,000
Stock-based compensation expense		$ 3,000.0	600,000	$ 100,000	2,100,000
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)		2,391,211		2,391,211
Number of shares forfeited (in shares)				166,023
Number of options outstanding (in shares)		891,211		891,211
2013 Plan | Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		1,500,000		1,500,000
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)							8,000,000
Number of shares forfeited (in shares)				331,638
Granted (in shares)				6,215,559
Number of options outstanding (in shares)		32,151		32,151
2021 Plan | Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		3,939,734		3,939,734
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)		832,950		832,950
Common stock, share reserve for issuance (in shares)		392,611		392,611
Granted (in shares)				507,340
Number of options outstanding (in shares)		602,355		602,355
Inducement Awards | Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		151,500		151,500
Visirna ESOP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	20,000,000
Granted (in shares)	7,500,000
Stock-based compensation expense		$ 900,000	$ 1,200,000	$ 1,900,000	$ 3,200,000