Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Securities available-for-sale at amortized cost	$ 593,381	$ 638,395
Securities held-to-maturity at fair value	1,651	1,644
Core deposit intangible, accumulated amortization	$ 8,324	$ 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)	17,536,914	17,466,375