Leases - Additional Information (Detail)	1 Months Ended	3 Months Ended	6 Months Ended
	Apr. 30, 2019 USD ($) ft² Option	Mar. 31, 2020 USD ($) ft² Option	Mar. 31, 2020 USD ($) ft² Option	Sep. 30, 2019 USD ($)
Lessee Lease Description [Line Items]
Estimated lease payments				$ 22,385,552
Estimated lease payments		$ 21,800,667	$ 21,800,667
Operating lease cost		500,000	900,000
Variable lease cost		200,000	300,000
Short-term lease cost		0	0
Operating lease cash payments		$ 300,000	$ 600,000
Weighted-average remaining lease term		8 years 7 months 6 days	8 years 7 months 6 days
Weighted-average discount rate		8.90%	8.90%
Research Facility in Madison | Wisconsin
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²		74,000	74,000
Operating lease renewal term		5 years	5 years
Number of options to renew | Option		2	2
Operating lease expiration month and year			2029-09
Estimated lease payments		$ 13,300,000	$ 13,300,000
Colorado Owner, LLC | Corporate Headquarters In Pasadena | California
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	$ 8,800,000
Expected leasehold improvements, net of tenant improvement allowances	$ 3,500,000
Operating lease renewal term	5 years
Number of options to renew | Option	1
Halozyme, Inc. | California | Sublease Agreement
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²		21,000	21,000
Estimated lease payments		$ 2,100,000	$ 2,100,000
Sublease commencement date		Apr. 01, 2020
Lease expiration date		Jan. 14, 2023