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Related-party Transactions (Details) ft² in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($) ft²	May 31, 2021 ft²
Related Party Transaction [Line Items]
Rentable area \| ft²					11
Affiliated Entity \| Sublease with Sonoma
Related Party Transaction [Line Items]
Rentable area \| ft²				18
Tenant improvements				$ 4.6
Due to related parties, current	$ 0.5
Due to related parties, noncurrent	3.9
Revenue recognized from related parties	$ 0.7
Affiliated Entity \| Sublease with Sonoma \| Minimum \| Lyell Immunopharma
Related Party Transaction [Line Items]
Ownership interest (as a percent)	5.00%
Investor \| GSK Agreement
Related Party Transaction [Line Items]
Due to related parties, current	$ 6.2		$ 5.0
Due to related parties, noncurrent	77.9		$ 79.7
Revenue recognized from related parties	$ 0.6	$ 2.4
Investor \| GSK Agreement \| Minimum \| Lyell Immunopharma \| GSK
Related Party Transaction [Line Items]
Ownership interest (as a percent)	10.00%