Condensed Consolidated Statements of Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Total
Balances at Dec. 31, 2017	$ 15	$ 238,246	$ (262,597)	$ (24,336)
Balances (in shares) at Dec. 31, 2017	14,946,712
Conversion of notes payable and related accrued interest and fees to common stock	$ 76	18,356		18,432
Conversion of notes payable and related accrued interest and fees to common stock (in shares)	76,007,754
Issuance of common stock	$ 18	2,583		2,601
Issuance of common stock (in shares)	18,253,320
Issuance of stock options for payment of accrued compensation		303		303
Stock-based compensation expense		2,675		2,675
Comprehensive loss			(5,087)	(5,087)
Balances at Mar. 31, 2018	$ 109	262,163	(267,684)	(5,412)
Balances (in shares) at Mar. 31, 2018	109,207,786
Balances at Dec. 31, 2017	$ 15	238,246	(262,597)	(24,336)
Balances (in shares) at Dec. 31, 2017	14,946,712
Issuance of common stock upon note conversions				18,432
Convertible note beneficial conversion feature
Comprehensive loss				(7,755)
Balances at Jun. 30, 2018	$ 110	263,173	(270,352)	(7,069)
Balances (in shares) at Jun. 30, 2018	109,696,119
Balances at Mar. 31, 2018	$ 109	262,163	(267,684)	(5,412)
Balances (in shares) at Mar. 31, 2018	109,207,786
Issuance of common stock	$ 1	179		180
Issuance of common stock (in shares)	400,000
Issuance of common stock in exchange for services		51		51
Issuance of common stock in exchange for services, shares	88,333
Stock-based compensation expense		780		780
Comprehensive loss			(2,668)	(2,668)
Balances at Jun. 30, 2018	$ 110	263,173	(270,352)	(7,069)
Balances (in shares) at Jun. 30, 2018	109,696,119
Balances at Dec. 31, 2018	$ 110	266,381	(274,601)	(8,110)
Balances (in shares) at Dec. 31, 2018	109,897,526
Issuance of stock options for payment of accrued compensation		195		195
Issuance of common stock for payment of accrued compensation		90		90
Issuance of common stock for payment of accrued compensation, shares	93,358
Issuance of common stock in exchange for services		68		68
Issuance of common stock in exchange for services, shares	82,432
Exercise of common stock options		50		50
Exercise of common stock options, shares	75,000
Stock-based compensation expense		697		697
Comprehensive loss			(2,541)	(2,541)
Balances at Mar. 31, 2019	$ 110	267,481	(277,142)	(9,551)
Balances (in shares) at Mar. 31, 2019	110,148,316
Balances at Dec. 31, 2018	$ 110	266,381	(274,601)	(8,110)
Balances (in shares) at Dec. 31, 2018	109,897,526
Issuance of common stock upon note conversions				981
Convertible note beneficial conversion feature				$ 142
Exercise of common stock options, shares				488,625
Comprehensive loss				$ (5,879)
Balances at Jun. 30, 2019	$ 113	269,606	(280,480)	(10,761)
Balances (in shares) at Jun. 30, 2019	112,741,563
Balances at Mar. 31, 2019	$ 110	267,481	(277,142)	(9,551)
Balances (in shares) at Mar. 31, 2019	110,148,316
Issuance of common stock upon note conversions	$ 2	979		981
Issuance of common stock upon note conversions, shares	2,179,622
Convertible note beneficial conversion feature		143		143
Exercise of common stock options	$ 1	274		275
Exercise of common stock options, shares	413,625
Stock-based compensation expense		729		729
Comprehensive loss			(3,338)	(3,338)
Balances at Jun. 30, 2019	$ 113	$ 269,606	$ (280,480)	$ (10,761)
Balances (in shares) at Jun. 30, 2019	112,741,563