Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	10,000,000	10,000,000
Common stock, issued (in shares)	7,738,167	7,600,167
Common stock, outstanding (in shares)	7,275,902	7,189,233
Treasury stock, shares (in shares)	462,265	410,934
Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.50	$ 0.50
Preferred stock, authorized (in shares)	700,000	700,000
Preferred stock, outstanding (in shares)	0	0