Stockholders' Equity (Stock-based Compensation Expense) (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
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| Share-based Compensation | $ 2,987 | $ 2,664 |
| General and Administrative [Member] | ||
| Share-based Compensation | 1,550 | 1,790 |
| Research and Development [Member] | ||
| Share-based Compensation | $ 1,437 | $ 874 |
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- Definition Amount of noncash expense for share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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