Summary of Significant Accounting Policies (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Summary of Significant Accounting Policies [Abstract]
Net loss	$ (13,885)	$ (10,315)	$ (35,118)	$ (30,608)
Weighted average common stock outstanding used to compute net loss per share, basic and diluted (in shares)	34,736,015	33,757,599	34,536,980	32,597,007
Net loss, basic and diluted (in USD per share)	$ (0.40)	$ (0.31)	$ (1.02)	$ (0.94)