Consolidated Statement of Stockholders' Equity - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total
Balances at Dec. 31, 2017	$ 95,000	$ 401,842,000	$ (394,206,000)
Balances (in shares) at Dec. 31, 2017	9,498,928
Common stock issued in registered public financings, net of offering costs (value)	$ 67,000	6,119,000
Common stock issued in registered public financings, net of offering costs (in shares)	6,743,640
Warrants exercised	$ 2,000	196,000
Warrants exercised (in shares)	217,400
Common stock issued under the employee stock purchase plan (value)		2,000
Common stock issued under the employee stock purchase plan (shares)	4,496
Warrant derivative liability reclassified to equity due to exercise of warrants		184,000
Stock-based compensation		122,000
Net loss			(3,134,000)	$ (3,134,000)
Balances at Mar. 31, 2018	$ 164,000	408,465,000	(397,340,000)
Balances (in shares) at Mar. 31, 2018	16,464,464
Balances at Dec. 31, 2018	$ 323,000	414,467,000	(406,316,000)	8,474,000
Balances (in shares) at Dec. 31, 2018	32,294,008
Warrants exercised	$ 5,000
Warrants exercised (in shares)	480,682
Stock-based compensation		99,000
Net loss			(3,617,000)	(3,617,000)
Balances at Mar. 31, 2019	$ 328,000	$ 414,566,000	$ (409,933,000)	$ 4,961,000
Balances (in shares) at Mar. 31, 2019	32,774,690