Balance Sheet Accounts - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 449,885	$ 444,053
Less: Accumulated depreciation and amortization	(62,816)	(58,021)
Property, plant and equipment, net	387,069	386,032
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,996	2,996
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	238,775	75,988
Research equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	68,868	65,353
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,574	0
Furniture
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,594	5,594
Computers and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,028	981
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	104,389	104,410
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 25,661	$ 188,731