Common Stock and Warrants (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Exchange of warrants	$ 0	$ 721,000
Public Aug 2017
Number of shares of common stock issued	5,500,000
Cash received from stock sale, before issuance costs	$ 11,500,000
Stock issuance costs	$ 1,100,000
Private Aug 2017
Number of shares of common stock issued	1,500,000
Cash received from stock sale, before issuance costs	$ 3,200,000
Stock issuance costs	23,000
Earlier Transaction
Exchange of warrants	$ 906,000
Exchange of warrants, shares	460,000
May 2017
Number of shares of common stock issued	1,700,000
Cash received from stock sale, before issuance costs	$ 3,700,000
Stock issuance costs	$ 125,000
June 2017
Number of shares of common stock issued	1,200,000
Cash received from stock sale, before issuance costs	$ 2,200,000
March 2016
Number of shares of common stock issued		4,100,000
Cash received from stock sale, before issuance costs		$ 6,900,000
Stock issuance costs		$ 650,000
Meyers Associates
Number of shares of common stock issued		498,000
Cash received from stock sale, before issuance costs		$ 845,000