Leases - Narrative (Details) ft² in Thousands, $ in Millions	12 Months Ended
	Sep. 30, 2024 USD ($) ft² option	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 25, 2023 USD ($)
Lessee Lease Description [Line Items]
Short-term lease cost | $	$ 0.0	$ 1.4	$ 0.3
Corporate Headquarters In Pasadena | California
Lessee Lease Description [Line Items]
Office space leases (in sq ft) | ft²	49
Corporate Headquarters In Pasadena | California | Colorado Owner, LLC
Lessee Lease Description [Line Items]
Number of options to renew | option	1
Operating lease renewal term	5 years
Research Facility in San Diego | California
Lessee Lease Description [Line Items]
Office space leases (in sq ft) | ft²	144
Operating lease renewal term	10 years
Lease term	15 years
Maximum additional tenant improvement allowance | $	$ 7.2			$ 23.6
Additional tenant improvement allowance interest per annum	7.00%			9.00%
Additional tenant improvement allowance liability | $	$ 3.1	$ 27.7
Research Facility in San Diego | California | Maximum
Lessee Lease Description [Line Items]
Number of options to renew | option	1
Research Facility in Madison | Wisconsin
Lessee Lease Description [Line Items]
Office space leases (in sq ft) | ft²	107
Number of options to renew | option	2
Operating lease renewal term	5 years