Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
STOCKHOLDERS' EQUITY
Accounts receivable, allowance	$ 790	$ 523
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized	8,000,000	8,000,000
Common stock, shares issued	4,838,071	4,838,071
Treasury stock, shares	1,497,957	1,487,238