Commitments and Contingencies - Additional Information (Detail)			1 Months Ended		3 Months Ended				9 Months Ended
	Sep. 17, 2018 USD ($) ft²	Sep. 07, 2016 USD ($)	Feb. 28, 2018 USD ($)	Nov. 30, 2009 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Loss Contingencies [Line Items]
Rent expense							$ 800,000	$ 700,000	$ 2,200,000	$ 1,700,000
Deferred rent							$ 1,100,000	$ 600,000	$ 1,100,000	$ 600,000
Maximum borrowing capacity			$ 175,000,000
Principal amount including interest paid in kind			$ 101,200,000
Debt maturity date			Dec. 31, 2023
Litigation settlement agreement date									September 7, 2016
Symphony Dynamo Holdings LLC
Loss Contingencies [Line Items]
License arrangement contingent consideration percentage				50.00%
License arrangement upfront payment				$ 50,000,000
Milestone payments									$ 0
Dynavax Technologies Securities Litigation
Loss Contingencies [Line Items]
Litigation amount payable		$ 4,100,000
Sublicense Agreement | Merck, Sharp & Dohme Corp.
Loss Contingencies [Line Items]
Payment upon obligation			$ 7,000,000
Scenario, Forecast | Sublicense Agreement | Merck, Sharp & Dohme Corp.
Loss Contingencies [Line Items]
Payment upon obligation					$ 7,000,000	$ 7,000,000
Office and Laboratory Space | Emeryville, California (Premises)
Loss Contingencies [Line Items]
Lease area | ft²	75,662
Base rent per square feet	$ 4.75
Operations commencement date	Apr. 01, 2019
Initial lease term	12 years
Lease option to extend	The Lease has an initial term of 12 years, following the Commencement Date with an option to extend the lease for two successive five-year terms
Renewal term of lease	5 years
Office and Laboratory Space | Emeryville, California (Premises) | Maximum
Loss Contingencies [Line Items]
Tenant improvement allowance	$ 8,300,000