Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Investment securities:
Securities held to maturity, fair value (in dollars)	$ 500	$ 2,556	$ 3,732
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50	$ 2.50
Common stock, shares authorized	80,000,000	80,000,000	40,000,000
Common stock, shares issued	36,723,238	36,759,656	29,267,369
Common stock, shares outstanding	36,723,238	36,759,656	29,267,369