Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 935	$ 1,131
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	18,857,000	18,312,000
Common stock, shares outstanding	18,857,000	18,312,000