Commitments and Contingencies (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Purchase commitments related to contract manufacturing, clinical development and certain other items	$ 8,000,000.0
Legal Matters
Loss Contingencies [Line Items]
Litigation matters, liabilities	0	$ 0
Indemnification Obligation
Loss Contingencies [Line Items]
Litigation matters, liabilities	0	0
Commercial Agreements
Loss Contingencies [Line Items]
Litigation matters, liabilities	0	$ 0
Merger and Acquisition Related Claims | Maximum
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	10,000,000.0
Securities Related Claims
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	10,000,000.0
Non-Securities Related Claims
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	$ 10,000,000.0