Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Securities available-for-sale at amortized cost	$ 573,660	$ 593,381
Securities held-to-maturity at fair value	1,662	1,651
Core deposit intangible, accumulated amortization	$ 8,364	$ 8,324
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)	17,553,490	17,536,914