Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Additional Paid-In Capital	Additional Paid-In Capital Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance
Stockholders' equity, beginning balance at Dec. 31, 2019	$ 301,728			$ 19,606		$ 335,355		$ 33,218			$ (6,357)		$ (80,094)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	28,332							28,332
Other Comprehensive Income (Loss)	6,104										6,104
Stock Dividend	0			588		15,818		(16,406)
Cash Dividends Paid	(11,710)							(11,710)
Stock Options Exercised, Net	596					344							252
Shares Issued Under the Directors' Stock	125					83							42
Shares Issued Under the Employee Stock Purchase Plan	392					260							132
Shares Issued for Dividend Reinvestment Plans	1,349					887							462
Stock-Based Compensation Expense	315					315
Purchases of Treasury Stock	(1,571)												(1,571)
Stockholders' equity, ending balance at Sep. 30, 2020	325,660			20,194		353,062		33,434			(253)		(80,777)
Stockholders' equity, beginning balance at Jun. 30, 2020	317,687			19,606		336,643		42,704			(276)		(80,990)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	11,046
Other Comprehensive Income (Loss)	23										23
Stock Dividend	0			588		15,818		(16,406)
Cash Dividends Paid	(3,910)							(3,910)
Stock Options Exercised, Net	188					107							81
Shares Issued Under the Employee Stock Purchase Plan	127					84							43
Shares Issued for Dividend Reinvestment Plans	457					304							153
Stock-Based Compensation Expense	106					106
Purchases of Treasury Stock	(64)												(64)
Stockholders' equity, ending balance at Sep. 30, 2020	325,660			20,194		353,062		33,434			(253)		(80,777)
Stockholders' equity, beginning balance at Dec. 31, 2020	334,392	$ 120	$ 334,512	20,194	$ 20,194	353,662	$ 353,662	41,899	$ 120	$ 42,019	(816)	$ (816)	(80,547)	$ (80,547)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	39,548							39,548
Other Comprehensive Income (Loss)	(2,903)										(2,903)
Stock Dividend	0			606		20,896		(21,502)
Cash Dividends Paid	(12,129)							(12,129)
Stock Options Exercised, Net	1,453					983							470
Shares Issued Under the Directors' Stock	284					208							76
Shares Issued Under the Employee Stock Purchase Plan	363					262							101
Shares Issued for Dividend Reinvestment Plans	1,366					1,028							338
Stock-Based Compensation Expense	310					310
Purchases of Treasury Stock	(2,633)												(2,633)
Stockholders' equity, ending balance at Sep. 30, 2021	360,171			20,800		377,349		47,936			(3,719)		(82,195)
Stockholders' equity, beginning balance at Jun. 30, 2021	353,033			20,194		355,195		60,494			(2,658)		(80,192)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	12,989							12,989
Other Comprehensive Income (Loss)	(1,061)										(1,061)
Stock Dividend	0			606		20,896		(21,502)
Cash Dividends Paid	(4,045)							(4,045)
Stock Options Exercised, Net	928					657							271
Shares Issued Under the Directors' Stock	95					71							24
Shares Issued Under the Employee Stock Purchase Plan	117					87							30
Shares Issued for Dividend Reinvestment Plans	455					340							115
Stock-Based Compensation Expense	103					103
Purchases of Treasury Stock	(2,443)												(2,443)
Stockholders' equity, ending balance at Sep. 30, 2021	$ 360,171			$ 20,800		$ 377,349		$ 47,936			$ (3,719)		$ (82,195)