Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss And Tax Credit Carryforward [Line Items]
Valuation allowance	$ 201,814	$ 174,921
Increase (decrease) in valuation allowance	26,900	93,700
Cumulative unrecognized tax benefits	6,867	$ 4,905	$ 3,351
Cumulative reduction to deferred tax assets related to net operating losses offset by valuation allowance	9,000
Unrecognized tax benefits that would impact effective tax rate	0
Federal
Operating Loss And Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 292,100
Operating loss carryforwards, expiration year	2020
Federal | Research and Development
Operating Loss And Tax Credit Carryforward [Line Items]
Research and development credits	$ 22,100
Research and development credits, expiration year	2032
State
Operating Loss And Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 187,700
Operating loss carryforwards, expiration year	2020
State | Research and Development
Operating Loss And Tax Credit Carryforward [Line Items]
Research and development credits	$ 17,000
Foreign | Research and Development
Operating Loss And Tax Credit Carryforward [Line Items]
Research and development credits	$ 900
Research and development credits, expiration year	2037