CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning Balance at Dec. 31, 2018	$ 7,157,000	$ 2,000	$ 243,022,000		$ (235,867,000)
Beginning Balance, shares at Dec. 31, 2018		2,148
Issuance of common stock for release of awards	(1,000)		(1,000)
Issuance of common stock for release of awards, shares		9
Stock-based compensation	(4,000)		(4,000)
Net income (loss)	10,000				10,000
Ending Balance at Mar. 31, 2019	7,162,000	$ 2,000	243,017,000		(235,857,000)
Ending Balance, shares at Mar. 31, 2019		2,157
Beginning Balance at Dec. 31, 2018	7,157,000	$ 2,000	243,022,000		(235,867,000)
Beginning Balance, shares at Dec. 31, 2018		2,148
Unrealized gain on available-for-sale investments	1,000
Net income (loss)	(1,894,000)
Ending Balance at Sep. 30, 2019	5,459,000	$ 2,000	243,217,000	$ 1,000	(237,761,000)
Ending Balance, shares at Sep. 30, 2019		2,178
Beginning Balance at Mar. 31, 2019	7,162,000	$ 2,000	243,017,000		(235,857,000)
Beginning Balance, shares at Mar. 31, 2019		2,157
Issuance of common stock for release of awards, shares		5
Stock-based compensation	119,000		119,000
Unrealized gain on available-for-sale investments	1,000			1,000
Net income (loss)	(103,000)				(103,000)
Ending Balance at Jun. 30, 2019	7,179,000	$ 2,000	243,136,000	1,000	(235,960,000)
Ending Balance, shares at Jun. 30, 2019		2,162
Issuance of common stock for release of awards	(3,000)		(3,000)
Issuance of common stock for release of awards, shares		16
Stock-based compensation	84,000		84,000
Net income (loss)	(1,801,000)				(1,801,000)
Ending Balance at Sep. 30, 2019	5,459,000	$ 2,000	243,217,000	$ 1,000	(237,761,000)
Ending Balance, shares at Sep. 30, 2019		2,178
Beginning Balance at Dec. 31, 2019	$ 4,836,000	$ 2,000	243,281,000		(238,447,000)
Beginning Balance, shares at Dec. 31, 2019	2,179	2,179
Issuance of common stock for release of awards	$ (1,000)		(1,000)
Issuance of common stock for release of awards, shares		20
Exercise of pre-funded warrants	2,000		2,000
Exercise of pre-funded warrants, shares		116
Stock-based compensation	68,000		68,000
Net income (loss)	(1,405,000)				(1,405,000)
Ending Balance at Mar. 31, 2020	3,500,000	$ 2,000	243,350,000		(239,852,000)
Ending Balance, shares at Mar. 31, 2020		2,315
Beginning Balance at Dec. 31, 2019	$ 4,836,000	$ 2,000	243,281,000		(238,447,000)
Beginning Balance, shares at Dec. 31, 2019	2,179	2,179
Deemed dividend for warrant exercise price adjustment	$ 392,000
Net income (loss)	(2,751,000)
Ending Balance at Sep. 30, 2020	$ 3,901,000	$ 3,000	245,488,000		(241,590,000)
Ending Balance, shares at Sep. 30, 2020	3,553	3,553
Beginning Balance at Mar. 31, 2020	$ 3,500,000	$ 2,000	243,350,000		(239,852,000)
Beginning Balance, shares at Mar. 31, 2020		2,315
Issuance of common stock for release of awards, shares		1
Sale of common stock, net of financing costs	1,619,000	$ 1,000	1,618,000
Sale of common stock, net of financing costs, shares		1,218
Deemed dividend for warrant exercise price adjustment	392,000		392,000		(392,000)
Stock-based compensation	66,000		66,000
Net income (loss)	(639,000)				(639,000)
Ending Balance at Jun. 30, 2020	4,546,000	$ 3,000	245,426,000		(240,883,000)
Ending Balance, shares at Jun. 30, 2020		3,534
Issuance of common stock for release of awards	(1,000)		(1,000)
Issuance of common stock for release of awards, shares		19
Stock-based compensation	63,000		63,000
Net income (loss)	(707,000)				(707,000)
Ending Balance at Sep. 30, 2020	$ 3,901,000	$ 3,000	$ 245,488,000		$ (241,590,000)
Ending Balance, shares at Sep. 30, 2020	3,553	3,553