Condensed Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Total revenues	$ 2,212	$ 1,595
Operating expenses:
Cost of product revenues	$ 352	$ 396
Type of cost, good or service [extensible list]	Product Revenue, Net [Member]	Product Revenue, Net [Member]
Research and development	$ 7,975	$ 7,587
Selling, general and administrative	3,531	3,431
Total operating expenses	11,858	11,414
Loss from operations	(9,646)	(9,819)
Other income (expense):
Interest and other income	37	258
Interest expense	(525)	(592)
Net other expense	(488)	(334)
Loss from continuing operations	(10,134)	(10,153)
Income from discontinued operations		205
Net loss	(10,134)	(9,948)
Net change in unrealized gain on available-for-sale securities, net of reclassification adjustments and taxes	(9)	(15)
Total comprehensive loss	$ (10,143)	$ (9,963)
Basic and diluted
Loss from continuing operations	$ (0.05)	$ (0.05)
Income from discontinued operations		0.00
Net loss per common share, basic and diluted	$ (0.05)	$ (0.05)
Weighted-average shares used in computing net income (loss) per share, basic and diluted	217,537	195,745
Collaborative Research and Development and Other Revenue [Member]
Total revenues	$ 574	$ (30)
Product Revenue, Net [Member]
Total revenues	$ 1,638	$ 1,625