Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Investment securities held-to-maturity, fair value	$ 133,519	$ 132,794
Common Stock, Par Value	$ 1.00	$ 1.00
Common Stock, Shares Authorized	20,000,000	20,000,000
Common Stock, Shares, Issued	8,514,547	8,511,835
Common Stock, Shares, Outstanding	8,416,095	8,419,183
Treasury Stock, Shares	98,452	92,652