Equity Incentive Plans (Allocation of Share-Based Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 938	$ 3,105
Research and development expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	1,013	1,794
General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ (75)	$ 1,311