Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 35,729	$ 30,006
Research and development credits	5,223	4,652
Stock-based compensation	322	173
Operating lease liabilities	661	909
Other	140	280
Total gross deferred tax assets	42,075	36,020
Less: Valuation allowance	(41,451)	(35,150)
Total deferred tax assets	624	870
Operating lease right-of-use assets	(624)	(870)
Total deferred tax liabilities	$ (624)	$ (870)