Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Loss before income taxes	$ 98,600,000	$ 39,200,000
Deferred tax assets, valuation allowance	78,065,000	49,975,000
Deferred tax assets, increase (decrease) in valuation allowance	28,100,000	13,200,000
Unrecognized tax benefits that would affect effective tax rate	0
Unrecognized tax benefits	3,345,000	$ 2,560,000	$ 1,809,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards available to offset future taxable income, amount	93,600,000
Federal | Tax Year 2018
Income Taxes [Line Items]
Net operating loss carryforwards	185,100,000
Federal | Tax Year 2018 | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards, amount	$ 4,500,000
Tax credit carryforwards, expiration year	2028
Federal | Tax Year 2018 | Orphan Drug
Income Taxes [Line Items]
Tax credit carryforwards, amount	$ 6,700,000
Tax credit carryforwards, expiration year	2036
Federal | Maximum | Tax Year 2018
Income Taxes [Line Items]
Percentage of utilization net operating loss carryforwards to taxable income	80.00%
Federal | Maximum | Prior to 2018
Income Taxes [Line Items]
Percentage of utilization net operating loss carryforwards to taxable income	100.00%
State
Income Taxes [Line Items]
Operating loss carryforwards available to offset future taxable income, amount	$ 125,700,000
State | Tax Year 2018
Income Taxes [Line Items]
Net operating loss carryforwards	$ 167,200,000
Percentage of utilization net operating loss carryforwards to taxable income	40.00%
Net operating loss carryforwards expiration beginning year	2029
State | Tax Year 2018 | Research and Development
Income Taxes [Line Items]
Tax credit carryforwards, amount	$ 400,000
Tax credit carryforwards, expiration year	2029