Income Taxes, Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets [Abstract]
Reserves and accruals	$ 62	$ 45
Research and development credits and other credits	1,730	1,635
Net operating loss carry forward	27,907	25,733
Stock based compensation	8,402	8,857
Other	11	26
Total deferred tax assets	38,112	36,296
Valuation allowance	(38,112)	(36,296)
Deferred tax assets after valuation allowance	0	0
Total deferred tax liability	0	0
Net deferred tax assets (liabilities)	$ 0	$ 0