UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Allowance for doubtful accounts	$ 113	$ 114
Shareholders’ equity:
Preferred stock - par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock - shares authorized (in shares)	960,000	960,000
Preferred stock - shares outstanding (in shares)	0	0
Common stock - par value (in dollars per share)	$ 0.10	$ 0.10
Common stock - shares authorized (in shares)	7,500,000	7,500,000
Common stock - shares outstanding (in shares)	4,251,015	4,243,716