Income Taxes - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Accrued interest and penalties related to uncertain tax positions	$ 0	$ 0	$ 0
Operating loss carry-forwards	37,300,000	8,700,000	37,300,000	$ 10,600,000
Tax reform, additional income tax benefit	100,000
Tax reform, additional tax expense	5,900,000
Tax reform, reduction of valuation allowance	5,900,000
Net deferred tax liabilities	0	0	0
(Benefit from) provision for income taxes		11,000	(115,000)	27,000
Deferred tax assets, operating loss carry-forwards	$ 8,610,000	10,793,000	$ 8,610,000	$ 9,239,000
Operating loss carry-forwards, subject to expiration		54,200,000
Scenario, forecast
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carry-forwards					$ 46,000,000
Research tax credit carry-forward
Operating Loss Carryforwards [Line Items]
Net operating loss carry-forwards		300,000
Domestic tax authority
Operating Loss Carryforwards [Line Items]
Operating loss carry-forwards		100,500,000
Deferred tax assets, operating loss carry-forwards		$ 46,000,000