Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Securities available-for-sale at amortized cost	$ 571,539	$ 638,395
Securities held-to-maturity at fair value	1,651	1,644
Core deposit intangible, accumulated amortization	$ 8,285	$ 8,138
Shareholders' equity:
Preferred stock, shares authorized (in shares)	300,000	300,000
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares outstanding (in shares)	17,513,449	17,466,375