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Income Taxes - Reconciliation of Total Income Tax Provision (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of the total income tax provision tax rate [Abstract]
Income tax expense (benefit) at federal statutory rate	(21.00%)	(34.00%)
Income tax expense (benefit) at state statutory rate	(8.20%)	(6.70%)
Change in valuation allowance	35.80%	(324.50%)
Change in state rate	(0.10%)	(1.50%)
Permanent interest adjustments	0.70%	0.40%
Stock compensation	1.80%	5.20%
Research credit	(1.40%)	(1.90%)
Foreign rate differential		350.40%
NOLs expiring and adjustments to NOL		12.10%
Mark to market adjustment	(5.30%)
Other, net	(2.30%)	0.50%
Total income tax provision	0.00%	0.00%

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Effective income tax rate reconciliation mark to market adjustment.

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Percentage 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 net operating loss expiration.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable permanent interest adjustments.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage 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 changes in the valuation allowance for deferred tax assets.

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Percentage 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 applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage 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 other adjustments.

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Percentage 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 research tax credit.

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