CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Available for sale securities, amortized cost	$ 153,765	$ 172,290
Held-to-maturity securities, fair value	$ 291,993	$ 281,310
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares, outstanding	4,850,230	4,107,051