Parent Company Financial Information, Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities [Abstract]
Net Income	$ 15,493	$ 14,810	$ 14,309	$ 14,122	$ 14,644	$ 13,738	$ 14,105	$ 13,549	$ 58,734	$ 56,036	$ 45,527
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities [Abstract]
Net Cash Provided by Operating Activities									58,119	80,858	57,774
Investing Activities [Abstract]
Net Cash Used in Investing Activities									(736,754)	(135,630)	(205,089)
Financing Activities [Abstract]
Stock Repurchased									(2,834)	0	(31,152)
Cash Dividends									(11,700)	(11,221)	(11,151)
Net Cash Provided by Financing Activities									767,714	203,966	105,730
Net Change in Cash and Cash Equivalents									89,079	149,194	(41,585)
Parent Company [Member]
Cash Flows from Operating Activities [Abstract]
Net Income									58,734	56,036	45,527
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities [Abstract]
(Equity) Loss in Undistributed Net Earnings from Subsidiary									(40,597)	(44,571)	26,488
Net (Increase) in Other Assets									(753)	(160)	(125)
Net Increase (Decrease) in Liabilities									360	222	(942)
Net Cash Provided by Operating Activities									17,744	11,527	70,948
Investing Activities [Abstract]
Payments for Business Acquisition									0	0	(28,642)
Payments for Investments in Non-Qualified Retirement Plan									(403)	(6,273)	(10,503)
Net Cash Used in Investing Activities									(403)	(6,273)	(39,145)
Financing Activities [Abstract]
Stock Repurchased									(2,834)	0	(31,152)
Issuance of Common Stock									403	6,973	10,503
Cash Dividends									(11,700)	(11,221)	(11,151)
Net Cash Provided by Financing Activities									(14,131)	(4,248)	(31,800)
Net Change in Cash and Cash Equivalents									3,210	1,006	3
Cash and Cash Equivalents at Beginning of Year				$ 1,341				$ 335	1,341	335	332
Cash and Cash Equivalents at End of Year	$ 4,551				$ 1,341				$ 4,551	$ 1,341	$ 335