Common Stock Issuance (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash received from stock sale, before issuance costs	$ 1,481,000	$ 1,168,000
December 2019 Agreement
Number of shares of common stock issued	7,000,000
Cash received from stock sale, before issuance costs	$ 2,400,000
Stock issuance costs	$ 90,000
Terms and provisions	In December 2019, we entered into a Common Stock Purchase Agreement with Lincoln Park granting us the right to sell shares of our common stock having an aggregate value of up to $16.0 million. Under the terms of the agreement, Lincoln Park made an initial purchase of 1.5 million shares of common stock for $1.0 million at a purchase price of $0.6531 per share. Subject to various limitations and conditions set forth in the agreement, we may sell up to an additional $15.0 million in shares of common stock, from time to time, at our sole discretion to Lincoln Park over a 24-month period beginning December 2019. In consideration for entering into the agreement, we issued 375,000 shares of our common stock, having a value of $277,000, based on the closing stock price at the date of grant, to Lincoln Park as a commitment fee. We incurred an additional $90,000 in issuance costs. As of March 31, 2020, we have issued 7.0 million shares and raised a total of $2.4 million under this agreement.
Registered January 2019
Number of shares of common stock issued	2,000,000
Cash received from stock sale, before issuance costs	$ 1,200,000
Stock issuance costs	$ 26,000
Terms and provisions	In January 2019, we raised $1.2 million before issuance costs of approximately $26,000 through a registered direct offering of 2.0 million shares of our common stock to a private investor.