Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Securities held for sale, at amortized cost, fair value	$ 10,533	$ 10,750
Common stock, par value	$ 1.25	$ 1.25
Common stock, shares authorized	20,000,000	20,000,000
Common stock, shares issued	6,975,734	7,126,541
Common stock, shares outstanding	6,975,734	7,126,541
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0