Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	37,221,098	37,200,698
Treasury stock, shares (in shares)	8,073,307	8,082,166