Income Taxes - Reconciliation of Income Taxes/(Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax benefit at U.S. federal statutory rate	$ (2,158)	$ (5,684)
Increase in domestic valuation allowance	4,815	5,914
State income taxes benefit before valuation allowance, net of federal benefit	(897)	6
State law change	1,418	0
Warrant revaluation income and other financing costs	(366)	(898)
Credits	(478)	(904)
Stock-based compensation	49	61
Return to provision true-ups	75	127
Capital loss carryforward expiration	0	817
Impact of federal rate change on valuation allowance	0	(34,463)
Other	56	6
Income tax expense (benefit)	0	0
State and Local Jurisdiction
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Impact of rate change	(2,514)	555
Domestic Tax Authority
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Impact of rate change	$ 0	$ 34,463

Effective Income Tax Rate Reconciliation, Capital Loss Carryforward Expiration

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Effective Income Tax Rate Reconciliation, Change In Enacted Laws, Amount

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Amount of increase in domestic valuation allowance during the period.

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Represents the amount pertaining to income tax reconciliation warrant revaluation and other finance (income) expense.

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State Income Tax Expense (Benefit) Before Valuation Allowance Net Of Federal Benefit.

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Amount of current tax expense (benefit) and deferred tax expense (benefit) pertaining to income (loss) from continuing operations and income (loss) from discontinued operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense (benefit).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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