Income Taxes - Valuation Allowance and Tax Reforms (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance
Increase in valuation allowance	$ 8,181	$ 17,504
Tax Reforms
Federal statutory income tax rate	21.00%	34.00%
Uncertain Tax Positions
Interest and penalties pertaining to uncertain tax positions	$ 0	$ 0

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

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- Definition

Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

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-Publisher FASB
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- References

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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