Stock-based Compensation (Summary of Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Stock-based Compensation
Shares, Balance Beginning	1,275,380
Shares, Granted	551,766
Shares, Exercised	(27,382)
Shares, Forfeited/Cancelled	(130,838)
Shares, Balance Ending	1,668,926	1,275,380
Vested and expected to vest at December 31, 2020	1,668,926
Exercisable at September 30, 2020	439,526
Weighted Average Exercise Price, Outstanding Beginning	$ 7.61
Weighted Average Exercise Price, Granted	3.38
Weighted Average Exercise Price, Exercised	3.15
Weighted Average Exercise Price, Forfeited/Cancelled	5.69
Weighted Average Exercise Price, Outstanding Ending	6.30	$ 7.61
Weighted Average Exercise Price, Vested or expected to vest at September 30, 2020	6.30
Weighted Average Exercise Price, Exercisable at September 30, 2020	$ 14.82
Weighted Average Remaining Contractual Term (Years), Outstanding	8 years 3 months 26 days	8 years 9 months 22 days
Weighted Average Remaining Contractual Term (Years), Vested or expected to vest at September 30, 2020	8 years 3 months 26 days
Weighted Average Remaining Contractual Term (Years), Exercisable at September 30, 2020	6 years 9 months
Aggregate Intrinsic Value, Exercised	$ 14

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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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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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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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 exercise price, at which grantee can acquire shares reserved for issuance, for 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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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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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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. 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 share options (or share units) exercised during the current period.

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