Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total		Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Retained Earnings		Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Unallo- cated ESOP Shares	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Beginning balance at Dec. 31, 2017		$ 249,603			$ 18,481	$ 290,219	$ 28,818			$ (200)	$ (8,514)	$ (331)	$ (79,201)
Beginning balance (Accounting Standards Update 2014-09) at Dec. 31, 2017				$ (102)					$ (102)			0
Beginning balance (Accounting Standards Update 2016-01) at Dec. 31, 2017				0					331			$ (331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		36,279					36,279
Other Comprehensive Income (Loss)		(4,965)									(4,965)
Stock Dividend		0	[1]		554	21,126	(21,680)	[1]
Cash Dividends Paid		(14,389)					(14,389)
Shares Issued for Stock Option Exercises, net		2,255				1,079							1,176
Shares Issued Under the Directors' Stock Plan		205				142							63
Shares Issued Under the Employee Stock Purchase Plan		505				340							165
Shares Issued for Dividend Reinvestment Plans		1,761				1,197							564
Stock-Based Compensation Expense		356				356
Purchases of Treasury Stock		(2,098)											(2,098)
Allocation of ESOP Stock		174				74				100
Ending balance at Dec. 31, 2018		$ 269,584		$ 0	19,035	314,533	29,257		$ 0	(100)	(13,810)		(79,331)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201409Member
Net Income		$ 37,475					37,475
Other Comprehensive Income (Loss)		7,453									7,453
Stock Dividend	[2]	0			571	17,737	(18,308)
Cash Dividends Paid	[1]	(15,206)					(15,206)
Shares Issued for Stock Option Exercises, net		1,792				877							915
Shares Issued Under the Directors' Stock Plan		258				177							81
Shares Issued Under the Employee Stock Purchase Plan		493				328							165
Shares Issued for Dividend Reinvestment Plans		1,777				1,232							545
Stock-Based Compensation Expense		391				391
Purchases of Treasury Stock		(2,469)											(2,469)
Allocation of ESOP Stock		180				80				100
Ending 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		40,827					40,827
Other Comprehensive Income (Loss)		5,541									5,541
Stock Dividend	[2]	0			588	15,818	(16,406)
Cash Dividends Paid	[1]	(15,740)					(15,740)
Shares Issued for Stock Option Exercises, net		748				433							315
Shares Issued Under the Directors' Stock Plan		125				83							42
Shares Issued Under the Employee Stock Purchase Plan		513				339							174
Shares Issued for Dividend Reinvestment Plans		1,808				1,214							594
Stock-Based Compensation Expense		420				420
Purchases of Treasury Stock		(1,578)											(1,578)
Ending balance at Dec. 31, 2020		$ 334,392			$ 20,194	$ 353,662	$ 41,899			$ 0	$ (816)		$ (80,547)

[1] Cash dividends paid per share have been adjusted for the September 25, 2020 3% stock dividend.

[2] Included in the shares issued for the 3% stock dividend in 2020 were treasury shares of 137,041