Consolidated Statement of Shareholders' Equity - 3 months ended Mar. 31, 2020 - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Restricted Shares	Restricted Shares Common Stock	Restricted Shares Treasury Stock
Balance, December 31, 2019 at Dec. 31, 2019	$ 594,393	$ 420,876	$ 187,149	$ (1,425)	$ (12,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(765)		(765)
Cash dividends declared	(7,038)		(7,038)
Reissuance of treasury stock for deferred compensation plan for Boards of Directors						$ 0	$ (1,865)	$ 1,865
Repurchase of treasury stock in connection with employee incentive plan and under compensation plan for Boards of Directors	(812)				(812)
Treasury Stock, Value, Acquired, Cost Method					(10,226)
Common shares issued under dividend reinvestment plan	209	209
Stock Issued During Period, Value, Employee Stock Purchase Plan	97	(8)			105
Share-based Compensation	1,380	1,380
Balance, March 31, 2020 at Mar. 31, 2020	583,721	420,678	175,637	8,252	(20,846)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Noncash Expense	240	45			195
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	9,677			$ 9,677
Stock Issued During Period, Value, Conversion of Units	$ 275	$ 41			$ 234
Cash dividends declared per common share	$ 0.34
Cumulative Effect on Retained Earnings, Net of Tax | Accounting Standards Update 2016-13 [Member]	$ (3,709)		$ (3,709)