Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Investment securities:
Securities held to maturity, fair value (in dollars)	$ 0	$ 0	$ 503
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	80,000,000
Common stock, shares issued	34,735,587	35,829,549	36,825,556
Common stock, shares outstanding	34,735,587	35,829,549	36,825,556