Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
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
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	15,000,000	15,000,000
Common stock, issued (in shares)	7,826,180	7,813,230
Common stock, outstanding (in shares)	7,344,955	7,339,578
Treasury stock, shares (in shares)	481,225	473,652
Series A Convertible Redeemable Preferred Stock
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.50	$ 0.50
Preferred stock, authorized (in shares)	150,000	150,000
Preferred stock, outstanding (in shares)	0	0
Series C Junior Participating Preferred Stock
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.50	$ 0.50
Preferred stock, authorized (in shares)	10,000	10,000
Preferred stock, outstanding (in shares)	0	0