Loans (Aging Of Recorded Investment In Past Due Loans) (Details) - USD ($) $ in Thousands		Sep. 30, 2020		Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		$ 12,501		$ 21,749
Past due nonaccrual loans and loans past due 90 days or more and accruing		23,200	[1]	26,535	[2]
Total loans past due		35,701		48,284
Total current		7,265,480		6,472,341
Recorded Investment		7,301,181		6,520,625
Loans past due 90 days or more and accruing		1,703		2,737
Impaired Financing Receivable, Recorded Investment, Nonaccrual loans which are current in regards to contractual P&I payments		101,600		66,300
Construction Real Estate Commercial [Domain]
Financing Receivable, Past Due [Line Items]
Past due nonaccrual loans and loans past due 90 days or more and accruing	[1]	38
Total loans past due		38
Total current		245,960		234,463
Recorded Investment		245,998		234,463
Loans past due 90 days or more and accruing		0		0
Commercial Financial And Agricultural [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		9		582
Past due nonaccrual loans and loans past due 90 days or more and accruing		11,949	[1]	12,407	[2]
Total loans past due		11,958		12,989
Total current		1,721,992		1,176,514
Loans past due 90 days or more and accruing		63		28
Construction Real Estate - Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		68		397
Total loans past due		68		397
Total current		112,829		96,405
Recorded Investment		112,897		96,802
Loans past due 90 days or more and accruing		0		0
Construction Real Estate - Installment [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days				24
Total loans past due				24
Total current		1,065		1,468
Recorded Investment		1,065		1,492
Loans past due 90 days or more and accruing		0		0
Residential Real Estate Commercial [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		119
Past due nonaccrual loans and loans past due 90 days or more and accruing		514	[1]	908	[2]
Total loans past due		633		908
Total current		502,148		479,512
Recorded Investment		502,781		480,420
Loans past due 90 days or more and accruing		0
Residential Real Estate - Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		6,246		12,841
Past due nonaccrual loans and loans past due 90 days or more and accruing		8,023	[1]	9,153	[2]
Total loans past due		14,269		21,994
Total current		1,104,784		1,155,703
Recorded Investment		1,119,053		1,177,697
Loans past due 90 days or more and accruing		476		1,209
Residential Real Estate - HELOC [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		725		652
Past due nonaccrual loans and loans past due 90 days or more and accruing		627	[1]	779	[2]
Total loans past due		1,352		1,431
Total current		193,661		224,448
Recorded Investment		195,013		225,879
Loans past due 90 days or more and accruing		65		44
Residential Real Estate - Installment [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		118		164
Past due nonaccrual loans and loans past due 90 days or more and accruing		89	[1]	338	[2]
Total loans past due		207		502
Total current		9,244		12,093
Recorded Investment		9,451		12,595
Loans past due 90 days or more and accruing		0
Commercial Financial And Agricultural [Member]
Financing Receivable, Past Due [Line Items]
Recorded Investment	[3]	1,733,950		1,189,503
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		717		160
Past due nonaccrual loans and loans past due 90 days or more and accruing		947	[1]	1,143	[2]
Total loans past due		1,664		1,303
Total current		1,694,624		1,613,681
Recorded Investment	[3]	1,696,288		1,614,984
Loans past due 90 days or more and accruing		654		625
Consumer [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		4,499		6,561
Past due nonaccrual loans and loans past due 90 days or more and accruing		947	[1]	1,621	[2]
Total loans past due		5,446		8,182
Total current		1,651,707		1,448,507
Recorded Investment		1,657,153		1,456,689
Loans past due 90 days or more and accruing		445		645
Finance Leases Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Accruing loans past due 30-89 days		0		368
Past due nonaccrual loans and loans past due 90 days or more and accruing		66	[1]	186	[2]
Total loans past due		66		554
Total current		27,466		29,547
Recorded Investment		27,532		30,101
Loans past due 90 days or more and accruing		$ 0		$ 186

[1] 1) Includes an aggregate of $1.7 million of loans past due 90 days or more and accruing. The remaining loans were past due nonaccrual loans.(2) Includes an aggregate of $101.6 million of nonaccrual loans which were current in regards to contractual principal and interest payments

[2] 1) Includes an aggregate of $2.7 million of loans past due 90 days or more and accruing. The remaining loans were past due nonaccrual loans.    (2) Includes an aggregate of $66.3 million of nonaccrual loans which were current in regards to contractual principal and interest payments.

[3] Included within each of commercial, financial and agricultural loans and commercial real estate loans is an immaterial amount of consumer loans that are not broken out by class.