Loans (Aging Of Recorded Investment In Past Due Loans) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		$ 20,109			$ 25,241
Past due nonaccrual loans and loans past due 90 days or more and accruing		27,626	[1]		17,776	[2]
Total loans past due		47,735			43,017
Total current		5,260,240			5,346,125
Recorded Investment		5,307,975			5,389,142
Loans past due 90 days or more and accruing		1,406			1,845
Impaired Financing Receivable, Recorded Investment, Nonaccrual loans which are current in regards to contractual P&I payments		39,900			56,100
Financing Receivable, Modifications, Recorded Investment, During Period		1,835		$ 8,085
Construction Real Estate Commercial [Domain]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days					29
Total loans past due					29
Total current		126,936			125,761
Recorded Investment		126,936			125,790
Loans past due 90 days or more and accruing		0			0
Financing Receivable, Modifications, Recorded Investment, During Period		63
Commercial Financial And Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		1,483			145
Past due nonaccrual loans and loans past due 90 days or more and accruing		13,100	[1]		1,043	[2]
Total loans past due		14,583			1,188
Total current		990,446			1,056,678
Loans past due 90 days or more and accruing		0
Financing Receivable, Modifications, Recorded Investment, During Period		55		4,098
Construction Real Estate - Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		84			256
Total loans past due		84			256
Total current		51,414			52,080
Recorded Investment		51,498			52,336
Loans past due 90 days or more and accruing		0			0
Construction Real Estate - Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		49			54
Past due nonaccrual loans and loans past due 90 days or more and accruing		3	[1]		19	[2]
Total loans past due		52			73
Total current		3,203			3,818
Recorded Investment		3,255			3,891
Loans past due 90 days or more and accruing		0			0
Residential Real Estate - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		413			16
Past due nonaccrual loans and loans past due 90 days or more and accruing		1,023	[1]		1,586	[2]
Total loans past due		1,436			1,602
Total current		389,373			392,521
Recorded Investment		390,809			394,123
Loans past due 90 days or more and accruing		0
Financing Receivable, Modifications, Recorded Investment, During Period				2,140
Residential Real Estate - Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		9,465			11,515
Past due nonaccrual loans and loans past due 90 days or more and accruing		8,010	[1]		9,232	[2]
Total loans past due		17,475			20,747
Total current		1,081,018			1,091,195
Recorded Investment		1,098,493			1,111,942
Loans past due 90 days or more and accruing		669			568
Financing Receivable, Modifications, Recorded Investment, During Period		650		608
Residential Real Estate - HELOC [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		570			616
Past due nonaccrual loans and loans past due 90 days or more and accruing		729	[1]		876	[2]
Total loans past due		1,299			1,492
Total current		193,763			202,660
Recorded Investment		195,062			204,152
Loans past due 90 days or more and accruing		47			14
Financing Receivable, Modifications, Recorded Investment, During Period		339		206
Residential Real Estate - Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		268			239
Past due nonaccrual loans and loans past due 90 days or more and accruing		215	[1]		253	[2]
Total loans past due		483			492
Total current		17,136			18,087
Recorded Investment		17,619			18,579
Loans past due 90 days or more and accruing		0			7
Financing Receivable, Modifications, Recorded Investment, During Period		115		34
Commercial Financial And Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded Investment	[3]	1,005,029			1,057,866
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		210			856
Past due nonaccrual loans and loans past due 90 days or more and accruing		2,748	[1]		2,360	[2]
Total loans past due		2,958			3,216
Total current		1,157,652			1,168,674
Recorded Investment	[3]	1,160,610			1,171,890
Loans past due 90 days or more and accruing		0
Financing Receivable, Modifications, Recorded Investment, During Period		249		379
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		7,567			11,515
Past due nonaccrual loans and loans past due 90 days or more and accruing		1,798	[1]		2,407	[2]
Total loans past due		9,365			13,922
Total current		1,246,348			1,231,622
Recorded Investment		1,255,713			1,245,544
Loans past due 90 days or more and accruing		690			1,256
Financing Receivable, Modifications, Recorded Investment, During Period		364		620
Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past due 30-89 days		0			0
Past due nonaccrual loans and loans past due 90 days or more and accruing		0	[1]		0	[2]
Total loans past due		0			0
Total current		2,951			3,029
Recorded Investment		2,951			$ 3,029
Accruing Financing Receivable Modifications [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		429		3,585
Accruing Financing Receivable Modifications [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		63
Accruing Financing Receivable Modifications [Member] | Commercial Financial And Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period				3,079
Accruing Financing Receivable Modifications [Member] | Construction Real Estate - Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		0		0
Accruing Financing Receivable Modifications [Member] | Construction Real Estate - Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		0		0
Accruing Financing Receivable Modifications [Member] | Residential Real Estate - Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		0		0
Accruing Financing Receivable Modifications [Member] | Residential Real Estate - HELOC [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		251		200
Accruing Financing Receivable Modifications [Member] | Residential Real Estate - Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		102		34
Accruing Financing Receivable Modifications [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		13		272
Nonaccruing Financing Receivable Modifications [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		1,406		4,500
Nonaccruing Financing Receivable Modifications [Member] | Commercial Financial And Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		55		1,019
Nonaccruing Financing Receivable Modifications [Member] | Residential Real Estate - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period				2,140
Nonaccruing Financing Receivable Modifications [Member] | Residential Real Estate - Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		650		608
Nonaccruing Financing Receivable Modifications [Member] | Residential Real Estate - HELOC [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		88		6
Nonaccruing Financing Receivable Modifications [Member] | Residential Real Estate - Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		13
Nonaccruing Financing Receivable Modifications [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		249		379
Nonaccruing Financing Receivable Modifications [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Modifications, Recorded Investment, During Period		$ 351		$ 348

[1] 1) Includes $1.4 million of loans past due 90 days or more and accruing. The remaining loans were past due nonaccrual loans.(2) Includes $39.9 million of nonaccrual loans which were current in regards to contractual principal and interest payments

[2] 1) Includes $1.8 million of loans past due 90 days or more and accruing. The remaining loans were past due nonaccrual loans.(2) Includes $56.1 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.