Common Stock Issuance (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Apr. 30, 2019
Cash received from stock sale, before issuance costs	$ 5,644,000	$ (36,000)	$ 13,236,000	$ 16,540,000
Private July 2019
Number of shares of common stock issued			3,000,000
Cash received from stock sale, before issuance costs			$ 2,000,000
Stock issuance costs			$ 24,000
Terms and provisions			In July 2019, we raised $2.0 million before issuance costs of approximately $24,000 through a registered direct offering of 3.0 million shares of our common stock to a private investor.
Registered April 2019
Number of shares of common stock issued			2,300,000
Cash received from stock sale, before issuance costs			$ 2,000,000
Stock issuance costs			$ 34,000
Terms and provisions			In April 2019, we raised $2.0 million before issuance costs of approximately $34,000 through a registered direct offering of 2.3 million shares of our common stock to a private investor.
Common Stock Purchase Agreement April 2019
Cash received from stock sale, before issuance costs			$ 1,000,000
Shares Issued, Price Per Share					$ 0.98
Stock issuance costs			$ 92,000
Terms and provisions			In April 2019, we entered into a Common Stock Purchase Agreement with Lincoln Park Capital Fund, LLC (Lincoln Park) granting us the right to sell shares of our common stock having an aggregate value of up to $11.0 million. Under the terms of the agreement, Lincoln Park made an initial purchase of $1.0 million in shares of common stock at a purchase price of $0.98 per share. Subject to various limitations and conditions set forth in the agreement, we may sell up to an additional $10.0 million in shares of common stock, from time to time, at our sole discretion to Lincoln Park over a 24-month period beginning April 2019. In consideration for entering into the agreement, we issued 250,000 shares of our common stock, having a value of $258,000, based on the closing stock price at the date of grant, to Lincoln Park as a commitment fee. We incurred an additional $92,000 in issuance costs. As of September 30, 2019, we have issued 11.8 million shares and raised a total of $8.3 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 Shehnee Lawrence Farhi.
Public December 2018
Number of shares of common stock issued			7,000,000
Cash received from stock sale, before issuance costs			$ 4,200,000
Stock issuance costs			$ 524,000
Terms and provisions			In December 2018, we raised $4.2 million before issuance costs of approximately $524,000 through an underwritten public offering of 7.0 million shares of our common stock.
Public June 2018
Number of shares of common stock issued			14,400,000
Cash received from stock sale, before issuance costs			$ 18,000,000
Stock issuance costs			$ 1,400,000
Terms and provisions			In June 2018, we raised $18.0 million before issuance costs of approximately $1.4 million through an underwritten public offering of 14.4 million shares of our common stock.