Leases - Additional Information (Detail) $ in Thousands		1 Months Ended			2 Months Ended	12 Months Ended			17 Months Ended
	Oct. 23, 2020 USD ($) ft²	Mar. 31, 2020 USD ($) ft²	Apr. 30, 2019 USD ($) ft² Option	Jan. 31, 2016 ft²	Dec. 31, 2020 USD ($) ft² Option	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2020 USD ($) ft²
Lessee Lease Description [Line Items]
Estimated lease payments						$ 37,114
Operating lease cost						5,100	$ 2,400	$ 1,300
Variable lease cost						800	800	500
Short-term lease cost						0	0	0
Operating lease cash payments						$ 3,100	$ 1,800	$ 1,300
Weighted-average remaining lease term						8 years
Weighted-average discount rate						8.50%
California | Halozyme, Inc. | Sublease Agreement
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²		21,000
Lease expiration date		Jan. 14, 2023
Estimated lease payments		$ 2,000
Sublease commencement date		Apr. 01, 2020
Corporate Headquarters In Pasadena | California
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²	24,000
Payments for leasehold improvements, net of tenant improvement allowances	$ 4,000
Lease expansion commencement period	2021-07
Lease expansion expiration month and year	2027-04
Estimated lease payments	$ 6,900
Corporate Headquarters In Pasadena | California | Colorado Owner, LLC
Lessee Lease Description [Line Items]
Lease term			91 months
Office space leases, in square feet | ft²			24,000
Lease payments, commencement date			Sep. 30, 2019
Estimated lease payments			$ 8,700
Lease expiration date			Apr. 30, 2027
Payments for leasehold improvements, net of tenant improvement allowances			$ 3,500
Operating lease renewal term			5 years
Number of options to renew | Option			1
Research Facility in Madison | Wisconsin
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²				60,000
Lease expiration date				Sep. 30, 2026					Sep. 30, 2031
Operating lease renewal term					5 years
Number of options to renew | Option					2
Estimated lease payments					$ 1,200				$ 26,200
Additional office space for lease | ft²					10,743				40,000
Expected leasehold improvements, net of tenant improvement allowances									$ 11,000