Stockholder's Equity (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Stock option activity, number of shares
Outstanding options, beginning of period	732,190	1,381,843
Granted	330,000	430,500
Exercised	(75,022)	0
Forfeited	(183,848)	(1,080,153)
Outstanding options, end of period	803,320	732,190
Options vested and expected to vest	786,829
Exercisable	556,487
Weighted average exercise price per share
Outstanding options, beginning of period	$ 3.72	$ 14.85
Granted	2.75	2.291
Exercised	2.46
Forfeited	6.14	5.9
Outstanding options, end of period	2.89	$ 3.72
Options vested and expected to vest	2.9
Exercisable	$ 3.12
Additional disclosure
Options outstanding, weighted average remaining contractual term	8 years 5 months 5 days	8 years 2 months 1 day
Options vested and expected to vest, weighted average remaining contractual term	8 years 5 months 5 days
Options exercisable, weighted average remaining contractual term	8 years 3 months 22 days
Options outstanding, aggregate intrinsic value	$ 54	$ 56
Options vested and expected to vest, aggregate intrinsic value	51
Options exercisable, aggregate intrinsic value	$ 20

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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