Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Unrecognized tax benefits	$ 0	$ 0
Accrual for interest or penalties	0	0
Recognized interest and penalties	0	$ 0
Domestic Tax Authority
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	815,400,000
Domestic Tax Authority | Research Tax Credit Carryforward
Income Tax Disclosure [Line Items]
California research and development tax credit carryforwards	20,600,000
Domestic Tax Authority | Expiring 2026
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	567,000,000.0
California research and development tax credit carryforwards	20,600,000
Domestic Tax Authority | Carryforward Indefinitely
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	248,400,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	670,800,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax Disclosure [Line Items]
California research and development tax credit carryforwards	20,400,000
State and Local Jurisdiction | Expiring 2026
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	622,600,000
California research and development tax credit carryforwards	3,500,000
State and Local Jurisdiction | Carryforward Indefinitely
Income Tax Disclosure [Line Items]
Income tax net operating loss carryforwards	48,200,000
California research and development tax credit carryforwards	$ 16,900,000