Statements of Convertible Preferred Stock and Stockholders' Equity (Unaudited) - USD ($)	Convertible Preferred Stock [Member]	Series B 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			$ 35,793	26,813,524				26,849,317
Issuance of common stock and warrants, Shares			35,792,593
Share-based compensation			$ 382	465,611				465,993
Share-based compensation, shares			382,356
Components of net income (loss)						686,730		686,730
Employee stock purchase plan			$ 63	44,412				44,475
Employee stock purchase plan, Shares			63,484		1
Cumulative catchup for adoption of ASC 606						294,561	[1]	294,561	[1]
Ending Balance at Sep. 30, 2018	$ 5,960,475		$ 59,044	478,071,950	(205,999)	(476,151,517)		1,773,478
Ending Balance, Shares at Sep. 30, 2018	23,900		59,044,164
Beginning Balance at Jun. 30, 2018	$ 5,960,475		$ 58,933	477,910,692	(205,999)	(476,035,222)		1,728,404
Beginning Balance, Shares at Jun. 30, 2018	23,900		58,933,384
Issuance of common stock			$ 1					1
Issuance of common stock, shares			666
Share-based compensation			$ 88	145,461				145,549
Share-based compensation, shares			88,444
Components of net income (loss)						(116,295)		(116,295)
Employee stock purchase plan			$ 22	15,797				15,819
Employee stock purchase plan, Shares			21,670
Ending Balance at Sep. 30, 2018	$ 5,960,475		$ 59,044	478,071,950	(205,999)	(476,151,517)		1,773,478
Ending Balance, Shares at Sep. 30, 2018	23,900		59,044,164
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			$ 7,164	12,878,144				12,885,308
Issuance of common stock and warrants, Shares			7,163,760
Share-based compensation			$ 207	1,380,488				1,380,695
Share-based compensation, shares			206,962
Components of net income (loss)						(3,506,790)		(3,506,790)
Employee stock purchase plan			$ 32	54,770				54,802
Employee stock purchase plan, Shares			32,064
Preferred stock issuance		$ 5,610		10,626,328				10,631,938
Preferred stock issuance, shares		5,610,121
Preferred stock conversion	$ (30,726)		$ 216	$ 30,510				$ 30,726
Preferred stock conversion, shares	(120)		216,028
Ending Balance at Sep. 30, 2019	$ 5,929,749	$ 5,610	$ 66,677	$ 503,149,814	$ (205,999)	$ (480,228,280)		$ 22,787,822
Ending Balance, Shares at Sep. 30, 2019	23,780	5,610,121	66,677,111
Beginning Balance at Jun. 30, 2019	$ 5,948,953		$ 59,383	479,127,279	(205,999)	(480,272,028)		(1,291,365)
Beginning Balance, Shares at Jun. 30, 2019	23,855		59,383,038
Issuance of common stock			$ 7,117	12,928,623				12,935,740
Issuance of common stock, shares			7,117,276
Share-based compensation			$ 33	425,680				425,713
Share-based compensation, shares			32,500
Components of net income (loss)						43,748		43,748
Employee stock purchase plan			$ 8	22,836				22,844
Employee stock purchase plan, Shares			8,307
Preferred stock issuance		$ 5,610		10,626,328				10,631,938
Preferred stock issuance, shares		5,610,121
Preferred stock conversion	$ (19,204)		$ 136	19,068				19,204
Preferred stock conversion, shares	(75)		135,990
Ending Balance at Sep. 30, 2019	$ 5,929,749	$ 5,610	$ 66,677	$ 503,149,814	$ (205,999)	$ (480,228,280)		$ 22,787,822
Ending Balance, Shares at Sep. 30, 2019	23,780	5,610,121	66,677,111

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