Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Valuation allowance increase (decrease)	$ 24,264,000	$ 8,192,000	$ (8,489,000)
NOL carryforward, decrease			1,506,000
Net loss	(80,805,000)	(41,978,000)	(15,002,000)
Unrecognized tax benefits that would impact effective tax rate	0	0
Unrecognized tax benefits	2,159,000	1,663,000	1,057,000
Unrecognized tax benefits, income tax penalties and interest accrued	0	0
Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	8,638,000	6,655,000
Research and development credits, decrease			$ 32,000
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforward	195,133,000	$ 125,850,000
Increase (decrease) in operating loss carryforwards	$ 109,484,000