Consolidated Statements of Stockholders’ Equity - USD ($) shares in Thousands, $ 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, 2021			49,499
Beginning balance at Sep. 30, 2021	$ 580,821		$ 0	$ 1,190,828	$ 546	$ (610,553)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offerings, net of underwriting discounts, commissions and offering expenses (in shares)			5,227
Issuance of common stock in public offerings, net of underwriting discounts, commissions and offering expenses	269,822			269,822
Vesting of restricted stock units (in shares)			365
Issuance of shares under the employee stock purchase plan (in shares)			97
Issuance of shares under the employee stock purchase plan	4,010			4,010
Exercise of stock options (in shares)			486
Exercise of stock options	5,952			5,952
Repurchases of early exercised stock options (in shares)			0
Business acquisition (in shares)			988
Business acquisition	77,122			77,122
Stock-based compensation	79,664			79,664
Other comprehensive income (loss)	(2,389)				(2,389)
Repurchases of common stock for income tax withholding (in shares)			(139)
Repurchase of common stock for income tax withholdings	(7,754)			(7,754)
Net loss	(217,863)					(217,863)
Ending balance (in shares) at Sep. 30, 2022			56,523
Ending 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
Issuance of shares under the employee stock purchase plan (in shares)			217
Issuance of shares under the employee stock purchase plan	3,937			3,937
Exercise of stock options (in shares)			118
Exercise of stock options	1,379			1,379
Business acquisition (in shares)			277
Business acquisition	5,860			5,860
Stock-based compensation	30,821			30,821
Other comprehensive income (loss)	1,087				1,087
Repurchases of common stock for income tax withholding (in shares)			(226)
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		57,557
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
Issuance of shares under the employee stock purchase plan (in shares)	177		177
Issuance of shares under the employee stock purchase plan	$ 3,765			3,765
Exercise of stock options (in shares)	384		384
Exercise of stock options	$ 7,100			7,100
Stock-based compensation	51,007			51,007
Other comprehensive income (loss)	234				234
Repurchases of common stock for income tax withholding (in shares)			(137)
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		58,877
Ending balance at Sep. 30, 2024	$ 472,689		$ 0	$ 1,715,119	$ (522)	$ (1,241,908)