Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 1,028	$ 978
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	20,000,000	20,000,000
Common stock, shares issued	12,513,000	12,495,000
Common stock, shares outstanding	12,513,000	12,495,000