Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2016 change
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 43,219,000	$ 55,348,000
Decrease in deferred tax asset valuation allowance	12,100,000
Number of previous ownership changes | change			3
Unrecognized tax benefits	0	$ 0
Interest and penalty charges incurred	0
Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	119,800,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	124,200,000
Research and Development Tax Credit Carryforwards | Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	12,700,000
Research and Development Tax Credit Carryforwards | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	5,200,000
Investment Tax Credit Carryforwards | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 500,000