Consolidated Statement of Shareholders' Equity - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands	Total	Common Shares	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock	Restricted Shares	Restricted Shares Common Shares	Restricted Shares Treasury Stock
Balance, December 31, 2015 at Dec. 31, 2015	$ 419,789	$ 343,948	$ 90,790	$ (359)	$ (14,590)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,749		23,749
Other comprehensive income, net of tax	8,906			8,906
Cash dividends declared	(8,564)		(8,564)
Reissuance of treasury stock for deferred compensation plan for Boards of Directors	232				232	$ 0	$ (1,297)	$ 1,297
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation	(3)	(3)
Repurchase of common shares in connection with employee incentive and director compensation plans	369				(369)
Common shares repurchased under share repurchase program	(4,965)				(4,965)
Common shares issued under dividend reinvestment plan	326	326
Common shares issued under compensation plan for Boards of Directors	245	18			263
Common shares issued under employee stock purchase plan	(282)	(11)			(293)
Stock-based compensation expense	1,009	1,009
Balance, September 30, 2016 at Sep. 30, 2016	$ 440,637	$ 343,954	$ 105,975	$ 8,547	$ (17,839)