Stockholders' Equity (Stock-Based Compensation Expense Recognized) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 729	$ 780	$ 1,426	$ 3,455
Unrecognized compensation expense	1,700		$ 1,700
Weighted average period for recognition			1 year 4 months 24 days
Weighted average fair value of options granted			$ 0.82
General And Administrative Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	697	780	$ 1,394	3,254
Research And Development Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 32		$ 32	$ 201