Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Increase (decrease) in deferred tax asset valuation allowance	$ 22,163,000	$ 12,826,000
Percent maximum of federal taxable income to offset with net operating losses	80.00%
Unrecognized tax benefits	$ 2,019,000	1,436,000	$ 1,348,000	$ 615,000
Unrecognized tax benefits that would impact effective tax rate	0
Unrecognized tax benefits, income tax penalties and interest expense	0	$ 0	$ 0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	241,908,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	209,771,000
Research Tax Credit Carryforward | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Research and development tax credits	6,275,000
Research Tax Credit Carryforward | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Research and development tax credits	$ 3,463,000