Consolidated Balance Sheets - Unaudited (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Investment securities available for sale, at fair value, amortized cost	$ 543,314	$ 692,824
Investment securities held to maturity at amortized cost, fair value	$ 7,547	$ 7,851
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	24,453,417	24,360,049
Common stock, outstanding (in shares)	20,242,893	20,161,395
Treasury stock (in shares)	4,210,524	4,198,654

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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