Income Taxes - Components of the Net Deferred Tax (Liability) and Asset (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Deferred tax assets:
Net operating loss carryforwards	$ 102,716	$ 60,495
Capitalized research and development	156,015	75,208
Tax credits	85,428	66,407
Deferred revenue	81,556	59,441
Lease liabilities	27,999	25,382
Stock compensation	10,989	10,296
Accrued compensation	4,078	3,082
Intangible assets	1,384	1,523
Other	2,843	2,636
Total gross deferred tax assets	473,008	304,470
Valuation allowance	(448,867)	(284,626)
Deferred tax liabilities:
Fixed assets	(13,155)	(9,878)
Right-of-use assets	(10,792)	(9,966)
Unrealized gains	(194)	0
Total gross deferred tax liability	(24,141)	(19,844)
Net deferred tax assets (liabilities)	$ 0	$ 0