Consolidated Statement of Shareholders' Equity - 3 months ended Mar. 31, 2017 - 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, 2016 at Dec. 31, 2016	$ 435,261	$ 344,404	$ 110,294	$ (1,554)	$ (17,883)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,809		8,809
Other comprehensive income, net of tax	1,946			1,946
Cash dividends declared	(3,634)		(3,634)
Stock Issued During Period, Value, Stock Options Exercised	0	(6)			6
Reissuance of treasury stock for deferred compensation plan for Boards of Directors						$ 0	$ (1,559)	$ 1,559
Reissuance of treasury stock for deferred compensation plan for Boards of Directors	1				1
Repurchase of common shares in connection with employee incentive plan and for Boards of Directors compensation plan	288				(288)
Common shares issued under dividend reinvestment plan	128	128
Common shares issued under compensation plan for Boards of Directors	128	(37)			91
Common shares issued under employee stock purchase plan	(90)	25			(65)
Stock-based compensation expense	568	568
Balance, March 31, 2017 at Mar. 31, 2017	$ 443,009	$ 343,597	$ 115,469	$ 392	$ (16,449)