Parent Company Financial Statements (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Jun. 25, 2019	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
Net Income		$ 20,890	$ 14,593	$ 14,255	$ 12,472	$ 15,820	$ 13,064	$ 15,271	$ 15,067	$ 62,210	$ 59,222	$ 46,529
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:
Interest Receivable and Other Assets										(2,925)	(1,602)	2,211
Change in Other Liabilities										4,433	4,488	(162)
Equity Based Compensation										1,051	1,287	1,355
Excess Tax Benefit from Restricted Share Grant										3	25	32
Net Cash from Operating Activities										92,418	65,229	62,331
CASH FLOWS FROM INVESTING ACTIVITIES
Net Cash from Investing Activities										(346,078)	30,662	(38,798)
CASH FLOWS FROM FINANCING ACTIVITIES
Advances in Long-term Debt										0	89,214	25,000
Repayments of Long-term Debt										(40,625)	(65,171)	(40,155)
Issuance (Retirement) of Common Stock										(5,789)	0	0
Dividends Paid										(20,136)	(17,556)	(14,074)
Net Cash from Financing Activities										495,524	(88,557)	2,658
Net Change in Cash and Cash Equivalents										241,864	7,334	26,191
Cash and Cash Equivalents at Beginning of Year					103,884				96,550	103,884	96,550	70,359
Cash and Cash Equivalents at End of Year		345,748				103,884				345,748	103,884	96,550
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income										62,210	59,222	46,529
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:
Interest Receivable and Other Assets										(8,575)	31	1,588
Change in Other Liabilities										(142)	(406)	(163)
Equity Based Compensation										1,051	1,287	1,355
Excess Tax Benefit from Restricted Share Grant										3	25	32
Equity in Excess Undistributed Income of Subsidiaries										(23,827)	(16,988)	(42,016)
Net Cash from Operating Activities										30,720	43,171	7,325
CASH FLOWS FROM INVESTING ACTIVITIES
Cash Used for Business Acquisitions										0	(14,958)	(25,160)
Net Cash from Investing Activities										0	(14,958)	(25,160)
CASH FLOWS FROM FINANCING ACTIVITIES
Advances in Long-term Debt										0	39,213	25,000
Repayments of Long-term Debt	$ (25,000)									0	(25,000)	0
Issuance (Retirement) of Common Stock										(5,789)	0	0
Dividends Paid										(20,136)	(17,556)	(14,074)
Net Cash from Financing Activities										(25,925)	(3,343)	10,926
Net Change in Cash and Cash Equivalents										4,795	24,870	(6,909)
Cash and Cash Equivalents at Beginning of Year					$ 42,738				$ 17,868	42,738	17,868	24,777
Cash and Cash Equivalents at End of Year		$ 47,533				$ 42,738				$ 47,533	$ 42,738	$ 17,868