Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common stock	Additional paid-in capital	Accumulated other comprehensive income / (loss)	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Sep. 30, 2022			56,523,000
Beginning balance at Sep. 30, 2022	$ 789,385		$ 0	$ 1,619,644	$ (1,843)	$ (828,416)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)			648,000
Issuance of shares under the employee stock purchase plan (in shares)			217,000
Issuance of shares under the employee stock purchase plan	3,937			3,937
Exercise of stock options (in shares)			118,000
Exercise of stock options	1,379			1,379
Business acquisition (in shares)			277,000
Business acquisition	5,860			5,860
Stock-based compensation expense	30,821			30,821
Other comprehensive income (loss)	1,087				1,087
Repurchases of common stock for income tax withholding (in shares)			(226,000)
Repurchase of common stock for income tax withholdings	(4,419)			(4,419)
Net loss	(204,618)					(204,618)
Ending balance (in shares) at Sep. 30, 2023			57,557,000
Ending balance at Sep. 30, 2023	$ 623,432	$ (148)	$ 0	1,657,222	(756)	(1,033,034)	$ (148)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting standards update	Accounting Standards Update 2016-13 [Member]
Vesting of restricted stock units (in shares)			896,000
Issuance of shares under the employee stock purchase plan (in shares)			177,000
Issuance of shares under the employee stock purchase plan	$ 3,765			3,765
Exercise of stock options (in shares)			384,000
Exercise of stock options	7,100			7,100
Stock-based compensation expense	51,007			51,007
Other comprehensive income (loss)	234				234
Repurchases of common stock for income tax withholding (in shares)			(137,000)
Repurchase of common stock for income tax withholdings	(3,975)			(3,975)
Net loss	$ (208,726)					(208,726)
Ending balance (in shares) at Sep. 30, 2024	58,877,000		58,877,000
Ending balance at Sep. 30, 2024	$ 472,689		$ 0	1,715,119	(522)	(1,241,908)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)			1,260,000
Restricted common stock canceled (in shares)			(137,000)
Issuance of shares under the employee stock purchase plan (in shares)	144,000		144,000
Issuance of shares under the employee stock purchase plan	$ 4,213			4,213
Exercise of stock options (in shares)	484,000		488,000
Exercise of stock options	$ 9,343			9,343
Stock-based compensation expense	64,504			64,504
Other comprehensive income (loss)	(105)				(105)
Repurchase of common stock for income tax withholdings	(16)			(16)
Net loss	$ (77,670)					(77,670)
Ending balance (in shares) at Sep. 30, 2025	60,631,000		60,632,000
Ending balance at Sep. 30, 2025	$ 472,958		$ 0	$ 1,793,163	$ (627)	$ (1,319,578)