Commitments and Contingencies - Additional Information (Details) ft² in Thousands		12 Months Ended
	Dec. 20, 2021 USD ($) ft² a	Sep. 30, 2023 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)
Other Commitments [Line Items]
Contingent liabilities		$ 0		$ 0
Construction in progress		166,655,000		$ 56,373,000
Tax increment financing award	$ 16,000,000
Maximum state income tax credits under agreement	$ 2,500,000
State income tax credits		1,500,000
Technology License Commitments | ARO-ENaC and ARO-HIF2 Candidates
Other Commitments [Line Items]
Milestone payments			$ 2,400,000
Verona Technology Park | Wisconsin
Other Commitments [Line Items]
Land purchased (in acres) | a	13
Drug Manufacturing Facility | Wisconsin
Other Commitments [Line Items]
Planned area of site (in sq ft) | ft²	160
Laboratory And Office Facility | Wisconsin
Other Commitments [Line Items]
Planned area of site (in sq ft) | ft²	140
Facilities
Other Commitments [Line Items]
Construction in progress		166,200,000
Facilities | Minimum
Other Commitments [Line Items]
Amount intended to invest for buildout of facilities		120,000,000
Facilities | Maximum
Other Commitments [Line Items]
Amount intended to invest for buildout of facilities		$ 130,000,000