Income Taxes - Components of the Net Deferred Tax (Liability) and Asset (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Deferred tax assets:
Net operating loss carryforwards	$ 70,858	$ 102,716
Capitalized research and development	232,360	156,015
Tax credits	48,867	85,428
Deferred revenue	171,262	81,556
Lease liabilities	23,919	27,999
Stock compensation	9,184	10,989
Accrued compensation	4,254	4,078
Intangible assets	1,034	1,384
Other	948	2,843
Total gross deferred tax assets	562,686	473,008
Valuation allowance	(497,543)	(448,867)
Deferred tax liabilities:
Fixed assets	(30,503)	(13,155)
Right-of-use assets	(9,424)	(10,792)
Unrealized gains	(630)	(194)
Original Issue Discount	(24,586)	0
Total gross deferred tax liability	(65,143)	(24,141)
Net deferred tax assets (liabilities)	$ 0	$ 0