Condensed Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 160	$ 160
Percentage of noncumulative preferred stock	10.00%	10.00%
Preferred stock, par value	$ 50	$ 50
Preferred stock, shares authorized	640	640
Preferred stock, shares issued	640	640
Preferred stock, shares outstanding	640	640
Common stock, par value	$ 0.50	$ 0.50
Common stock, shares authorized	15,000,000	15,000,000
Common stock, shares issued	4,866,593	4,862,693
Common stock, shares outstanding	4,866,593	4,862,693