Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Held-to-maturity, fair value	$ 51,013	$ 9,225
Common stock, par value	$ 6.25	$ 6.25
Common stock, authorized shares	9,000,000	9,000,000
Common stock, shares issued	2,980,602	2,980,602
Common stock, shares outstanding	2,725,524	2,742,350
Treasury stock, at cost	255,078	238,252