Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax credit at statutory rates	$ (268)	$ (436)
Nondeductible expenses	2	2
State income tax, net of federal benefits	(45)	(66)
Effect of US tax rate change	9,284	0
Expiration of stock options	188	149
Other	0	(5)
Change in valuation allowance	$ (9,161)	$ 356