Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Unallocated ESOP Shares	Accumulated Other Comprehensive Loss	Treasury Stock
Stockholders' equity, beginning balance at Dec. 31, 2018	$ 269,584	$ 19,035	$ 314,533	$ 29,257	$ (100)	$ (13,810)	$ (79,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	27,735			27,735
Other Comprehensive Income	4,831					4,831
Stock Dividend	0	571	17,737	(18,308)
Cash Dividends Paid	(11,309)			(11,309)
Stock Options Exercised, Net	1,640		802				838
Shares Issued Under the Directors' Stock	130		86				44
Shares Issued Under the Employee Stock Purchase Plan	360		236				124
Shares Issued for Dividend Reinvestment Plans	1,333		911				422
Stock-Based Compensation Expense	292		292
Purchases of Treasury Stock	(2,368)						(2,368)
Stockholders' equity, ending balance at Sep. 30, 2019	292,228	19,606	334,597	27,375	(100)	(8,979)	(80,271)
Stockholders' equity, beginning balance at Jun. 30, 2019	284,649	19,035	316,229	39,397	(100)	(9,647)	(80,265)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	10,067			10,067
Other Comprehensive Income	668					668
Stock Dividend	0	571	17,737	(18,308)
Cash Dividends Paid	(3,781)			(3,781)
Stock Options Exercised, Net	315		164				151
Shares Issued Under the Employee Stock Purchase Plan	110		73				37
Shares Issued for Dividend Reinvestment Plans	429		296				133
Stock-Based Compensation Expense	98		98
Purchases of Treasury Stock	(327)						(327)
Stockholders' equity, ending balance at Sep. 30, 2019	292,228	19,606	334,597	27,375	(100)	(8,979)	(80,271)
Stockholders' equity, beginning balance at Dec. 31, 2019	301,728	19,606	335,355	33,218	0	(6,357)	(80,094)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	28,332			28,332
Other Comprehensive Income	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	0	(253)	(80,777)
Stockholders' equity, beginning balance at Jun. 30, 2020	317,687	19,606	336,643	42,704	0	(276)	(80,990)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	11,046			11,046
Other Comprehensive Income	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	$ 0	$ (253)	$ (80,777)