Income Taxes - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Accrued interest and penalties related to uncertain tax positions	$ 0	$ 0	$ 0
Operating loss carry-forwards			10,600,000
Tax reform, additional income tax benefit	125,000
Tax reform, additional tax expense	5,900,000
Tax reform, reduction of valuation allowance	5,900,000
Deferred tax assets, operating loss carry-forwards	8,610,000	8,610,000	9,239,000	$ 5,384,000
Operating loss carry-forwards, subject to expiration	54,200,000	54,200,000
Net deferred tax liabilities	0	0	0
(Benefit from) provision for income taxes		(115,000)	$ 27,000	$ 149,000
Scenario, forecast
Operating Loss Carryforwards [Line Items]
Operating loss carry-forwards					$ 37,300,000
Research tax credit carry-forward
Operating Loss Carryforwards [Line Items]
Net operating loss carry-forwards	299,000	299,000
Domestic tax authority
Operating Loss Carryforwards [Line Items]
Operating loss carry-forwards	91,800,000	91,800,000
Deferred tax assets, operating loss carry-forwards	$ 37,300,000	$ 37,300,000