Leases - Additional Information (Detail)		1 Months Ended			2 Months Ended	3 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	Dec. 31, 2020 USD ($) Option	Dec. 31, 2019 USD ($)	May 31, 2020 USD ($) ft²
Lessee Lease Description [Line Items]
Estimated lease payments					$ 31,596,000	$ 31,596,000
Operating lease cost						900,000	$ 500,000
Variable lease cost						200,000	200,000
Short-term lease cost						0	0
Operating lease cash payments						$ 700,000	$ 300,000
Weighted-average remaining lease term					9 years 2 months 12 days	9 years 2 months 12 days
Weighted-average discount rate					8.40%	8.40%
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		$ 2,000,000.0
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
Lease commencement period	2021-07
Lease expiration month and year	2027-04
Estimated lease payments	$ 6,900,000
Expected leasehold improvements, net of tenant improvement allowances	$ 4,000,000.0
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			$ 8,700,000
Lease expiration date			Apr. 30, 2027
Payments for leasehold improvements, net of tenant improvement allowances			$ 3,500,000
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	5 years
Number of options to renew | Option					2	2
Estimated lease payments					$ 1,200,000	$ 1,200,000		$ 26,200,000
Expected leasehold improvements, net of tenant improvement allowances								$ 11,000,000.0
Additional office space for lease | ft²					10,743			40,000