Parent Only Financial Information Parent Only Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities:
Net Income	$ 40,827	$ 37,475	$ 36,279
Shares Issued Under the Directors’ Stock Plan	125	258	205
Net Cash Provided By Operating Activities	42,314	43,944	41,976
Cash Flows from Financing Activities:
Shares Issued for Stock Option Exercises, net	748	1,792	2,255
Shares Issued Under the Employee Stock Purchase Plan	513	493	505
Shares Issued for Dividend Reinvestment Plans	1,808	1,777	1,761
Purchase of Treasury Stock	(1,578)	(2,469)	(2,098)
Cash Dividends Paid	(15,740)	(15,206)	(14,389)
Net Cash Provided By Financing Activities	455,773	134,269	197,195
Net Increase (Decrease) in Cash and Cash Equivalents	310,770	(14,018)	11,401
Cash and Cash Equivalents at Beginning of Year	70,221	84,239	72,838
Cash and Cash Equivalents at End of Year	380,991	70,221	84,239
Interest on Deposits and Borrowings	13,799	20,843	12,212
Parent Company
Cash Flows from Operating Activities:
Net Income	40,827	37,475	36,279
Undistributed Net Income of Subsidiaries	(24,526)	(23,753)	(23,489)
Shares Issued Under the Directors’ Stock Plan	125	258	205
Changes in Other Assets and Other Liabilities	(3,606)	(1,236)	(918)
Net Cash Provided By Operating Activities	12,820	12,744	12,077
Cash Flows from Financing Activities:
Shares Issued for Stock Option Exercises, net	748	1,792	2,255
Shares Issued Under the Employee Stock Purchase Plan	513	493	505
Shares Issued for Dividend Reinvestment Plans	1,808	1,777	1,761
Purchase of Treasury Stock	(1,578)	(2,469)	(2,097)
Cash Dividends Paid	(15,740)	(15,206)	(14,389)
Net Cash Provided By Financing Activities	(14,249)	(13,613)	(11,965)
Net Increase (Decrease) in Cash and Cash Equivalents	(1,429)	(869)	112
Cash and Cash Equivalents at Beginning of Year	1,429	2,298	2,186
Cash and Cash Equivalents at End of Year	0	1,429	2,298
Interest on Deposits and Borrowings	$ 746	$ 1,024	$ 976