Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Valuation allowances recognized in the current year	$ 9,200,000	$ 2,900,000
Internal Revenue Code related to annual use of operating loss carry forwards	annual use of the Company’s net operating loss and research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a rolling three-year period
Income tax benefit recognized related to uncertain tax positions	$ 0	0
Interest expense related to uncertain tax positions	0	0
Liability related to unrecognized tax benefits	0	$ 0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	389,100,000
Operating loss carryforwards, not subject to expiration	41,300,000
Research and development tax credit carryforwards	10,200,000
California Franchise Tax Board
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	44,000,000.0
Research and development tax credit carryforwards	12,100,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 50,200,000