Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Series B redeemable convertible preferred stock [Member]	Total
Balances at Dec. 31, 2014	$ 40,000	$ 365,403,000	$ (362,006,000)	$ 1,990,000	$ 3,437,000
Balances (in shares) at Dec. 31, 2014	3,983,182			8,671,040
Net loss			(516,000)		(516,000)
Accretion of dividends on Series B redeemable convertible preferred stock		(1,307,000)		$ 1,307,000	(1,307,000)
Accretion to redemption value of Series B redeemable convertible preferred stock		(8,971,000)		8,971,000	(8,971,000)
Conversion of Series B redeemable convertible preferred stock to common stock, value	$ 2,000	1,504,000		$ (378,000)	1,506,000
Conversion of Series B redeemable convertible preferred stock to common stock, shares	228,637			(1,143,187)
Common stock issued in financing, net of offering costs	$ 16,000	8,250,000			8,266,000
Common stock issued in financing, net of offering costs (in shares)	1,575,758
Warrants exercised	$ 1,000	1,072,000			1,073,000
Warrants exercised (in shares)	56,645
Warrants reclassified from liabilities to equity due to amendment of warrants		5,462,000			5,462,000
Warrants reclassified from liabilities to equity due to increase in authorized shares		3,281,000			$ 3,281,000
Exercise of common stock options (shares)	39,281				214,815
Stock-based compensation		479,000			$ 479,000
Stock-based compensation - severance		4,000			4,000
Balances at Dec. 31, 2015	$ 59,000	375,177,000	(362,522,000)	$ 11,890,000	12,714,000
Balances (in shares) at Dec. 31, 2015	5,883,503			7,527,853
Net loss			(18,838,000)		(18,838,000)
Accretion of dividends on Series B redeemable convertible preferred stock		(365,000)		$ 365,000	(365,000)
Accretion to redemption value of Series B redeemable convertible preferred stock		(1,493,000)		1,493,000	(1,493,000)
Conversion of Series B redeemable convertible preferred stock to common stock, value	$ 24,000	10,605,000		$ (13,748,000)	10,629,000
Conversion of Series B redeemable convertible preferred stock to common stock, shares	2,359,025			(7,527,853)
Warrants issued for Novolytics assets (value)		204,000			204,000
Common stock issued in June 2016 financing, net of offering costs and warrants (value)	$ 21,000	2,613,000			2,634,000
Common stock issued in June 2016 financing, net of offering costs and warrants (shares)	2,127,660
Common stock issued in November 2016 financing, net of offering costs and warrants (value)	$ 53,000	632,000			685,000
Common stock issued in November 2016 financing, net of offering costs and warrants (shares)	5,335,000
Common stock issued pursuant to anti-dilution rights (value)	$ 7,000	1,538,000			1,545,000
Common stock issued pursuant to anti-dilution rights (shares)	750,206
Common stock issued under the employee stock purchase plan (value)	$ 1,000	12,000			13,000
Common stock issued under the employee stock purchase plan (shares)	32,726
Stock-based compensation		1,995,000			1,995,000
Balances at Dec. 31, 2016	$ 165,000	$ 390,918,000	$ (381,360,000)		$ 9,723,000
Balances (in shares) at Dec. 31, 2016	16,488,120