CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Cash and due from banks, interest-bearing amounts	$ 68,018	$ 61,965
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	36,130,480	36,130,480
Common stock, shares outstanding (in shares)	35,006,587	34,971,929
Treasury stock, shares (in shares)	1,123,893	1,158,551