Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
ASSETS
Other physical property, accumulated depreciation	$ 422	$ 410
CURRENT ASSETS:
Accounts receivables, reserves	$ 343	$ 305
COMMON STOCKHOLDERS' EQUITY:
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized (in shares)	46,500,000	46,500,000
Common stock, issued (in shares)	12,974,287	12,943,536
Common stock, outstanding (in shares)	12,974,287	12,943,536
Preferred stock, authorized (in shares)	500,000	500,000
Preferred stock, issued (in shares)	0	0