Statements of Convertible Preferred Stock and Stockholders' Equity (Unaudited) - USD ($)	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]		Total
Beginning Balance at Dec. 31, 2017	$ 5,960,475	$ 22,806	$ 450,748,403	$ (205,999)	$ (477,132,808)		$ (26,567,598)
Beginning Balance, Shares at Dec. 31, 2017	23,900	22,805,731
Issuance of common stock and warrants		$ 35,792	26,893,991				26,929,783
Issuance of common stock and warrants, Shares		35,791,927
Share-based compensation		$ 286	$ 216,388				216,674
Share-based compensation, shares		285,662
Components of net income (loss)					$ 1,435,228		1,435,229
Employee stock purchase plan		$ 17	13,514				13,531
Employee stock purchase plan, Shares		17,806
Cumulative catchup for adoption of ASC 606					$ 294,562	[1]	294,562	[1]
Ending Balance at Mar. 31, 2018	$ 5,960,475	$ 58,901	477,872,296	(205,999)	(475,403,018)		2,322,180
Ending Balance, Shares at Mar. 31, 2018	23,900	58,901,126
Beginning Balance at Dec. 31, 2018	$ 5,960,475	$ 59,058	478,179,574	$ (205,999)	$ (476,721,490)		$ 1,311,143
Beginning Balance, Shares at Dec. 31, 2018	23,900	59,058,297
Issuance of common stock and warrants		$ 33	$ 16,390				$ 16,423
Issuance of common stock and warrants, Shares		33,087
Share-based compensation		$ 167	$ 147,787				$ 147,954
Share-based compensation, shares		166,962
Components of net income (loss)					$ (2,122,820)		$ (2,122,820)
Employee stock purchase plan		$ 15	$ 15,049				$ 15,064
Employee stock purchase plan, Shares		14,625
Preferred stock conversion	$ (5,121)	$ 35	$ 5,086				$ 5,121
Preferred stock conversion, shares	(20)	35,266
Ending Balance at Mar. 31, 2019	$ 5,955,354	$ 59,308	$ 478,363,886	$ (205,999)	$ (478,844,310)		$ (627,115)
Ending Balance, Shares at Mar. 31, 2019	23,880	59,308,237

[1] Represents the adjustments related to the adoption of new accounting standards. See Note 2 for details.