Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Restricted Shares	Common Shares	Common Shares Restricted Shares	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Treasury Stock Restricted Shares
Balance, December 31, 2020 at Dec. 31, 2019	$ 594,393		$ 420,876		$ 187,149	$ (1,425)	$ (12,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,984				3,984
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	6,059					6,059
Cash dividends declared	(13,852)				(13,852)
Reissuance of treasury stock for common share awards		$ 0		$ (2,262)				$ 2,262
Reissuance of treasury stock for deferred compensation plan for Boards of Directors	59						59
Repurchase of treasury stock in connection with employee incentive program and compensation plan for Boards of Directors	(986)						(986)
Treasury Stock, Value, Acquired, Cost Method							(20,000)
Common shares issued under dividend reinvestment plan	243		243
Share-based Payment Arrangement, Noncash Expense	273		20				253
Stock Issued During Period, Value, Employee Stock Purchase Plan	199		(17)				216
Share-based Compensation	2,335		2,335
Balance, June 30, 2021 at Jun. 30, 2020	569,177		421,236		173,572	4,634	(30,265)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Conversion of Units	179		41				138
Balance, December 31, 2020 at Dec. 31, 2020	575,673		422,536		190,691	1,336	(38,890)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,566				25,566
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(3,558)					(3,558)
Cash dividends declared	(13,898)				(13,898)
Reissuance of treasury stock for common share awards		$ 0		$ (2,172)				$ 2,172
Reissuance of treasury stock for deferred compensation plan for Boards of Directors	74						74
Repurchase of treasury stock in connection with employee incentive program and compensation plan for Boards of Directors	(998)						(998)
Common shares issued under dividend reinvestment plan	378		378
Share-based Payment Arrangement, Noncash Expense	249		65				184
Stock Issued During Period, Value, Employee Stock Purchase Plan	235		61				174
Share-based Compensation	1,784		1,784
Balance, June 30, 2021 at Jun. 30, 2021	$ 585,505		$ 422,652		$ 202,359	$ (2,222)	$ (37,284)