Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
ASSETS
Other physical property, accumulated depreciation	$ 400	$ 387
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)	12,914,267	12,872,742
Common stock, outstanding (in shares)	12,914,267	12,872,742
Preferred stock, authorized (in shares)	500,000	500,000
Preferred stock, issued (in shares)	0	0