Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Investment securities:
Securities held to maturity, fair value (in dollars)	$ 503	$ 2,556	$ 4,248
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	36,825,556	36,759,656	29,259,264
Common stock, shares outstanding	36,825,556	36,759,656	29,259,264