CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value per share	$ 2.50	$ 2.50
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 2.50	$ 2.50
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	2,728,327	2,714,273
Common stock, nonvested shares issued	36,179	25,268
Common stock, shares outstanding	2,728,327	2,714,273