Stockholders' Equity (Stock-Based Compensation Expense Recognized) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 357	$ 729	$ 622	$ 1,426
Unrecognized compensation expense	1,000		$ 1,000
Weighted average period for recognition			1 year 4 months 24 days
General And Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	295	697	$ 506	1,394
Research And Development Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 62	$ 32	$ 116	$ 32