Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
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)	7,796,230	7,738,167
Common stock, outstanding (in shares)	7,331,917	7,275,902
Treasury stock, shares (in shares)	464,313	462,265
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