Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Net operating loss carryforwards and capital loss carryforwards	$ 15,204	$ 11,414
Research and development credit carryforwards	2,444	2,141
Marketable equity securities	393
Patents and fixed assets	523	268
Stock-based and other compensation	1,326	1,260
Total	19,890	15,083
Valuation Allowance	(19,890)	(15,083)
Net deferred tax asset (liability)

Patents and fixed assets.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from equity method investments.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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