Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	26,725,620	26,658,032
Treasury stock, shares	4,208,867	4,185,242