Allowance For Loan Losses (Activity In The Allowance For Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Reserve Estimate Methodology, Historical Loss Period Factor			96 months	84 months
Financing Receivable, Allowance for Credit Losses, Write-downs	$ 3,450	$ 3,708
Financing Receivable, Allowance for Credit Losses, Recovery	2,171	2,130
Financing Receivables Allowance For Credit Losses Net Charge Offs	1,279	1,578
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	49,988	50,624	$ 50,624
Ending balance	48,969	49,922	49,988	$ 50,624
Provision for Loan, Lease, and Other Losses	260	876
Commercial Financial And Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	649	339
Financing Receivable, Allowance for Credit Losses, Recovery	652	369
Financing Receivables Allowance For Credit Losses Net Charge Offs	(3)	(30)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	15,022	13,434	13,434
Ending balance	14,077	13,437	15,022	13,434
Provision for Loan, Lease, and Other Losses	(948)	(27)
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	47	112
Financing Receivable, Allowance for Credit Losses, Recovery	87	114
Financing Receivables Allowance For Credit Losses Net Charge Offs	(40)	(2)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	9,601	10,432	10,432
Ending balance	9,488	10,281	9,601	10,432
Provision for Loan, Lease, and Other Losses	(153)	(153)
Construction Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	0	27
Financing Receivable, Allowance for Credit Losses, Recovery	59	58
Financing Receivables Allowance For Credit Losses Net Charge Offs	(59)	(31)
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,430	5,247	5,247
Ending balance	4,463	4,368	4,430	5,247
Provision for Loan, Lease, and Other Losses	(26)	(910)
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	116	480
Financing Receivable, Allowance for Credit Losses, Recovery	360	291
Financing Receivables Allowance For Credit Losses Net Charge Offs	(244)	189
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	9,321	10,958	10,958
Ending balance	9,415	10,745	9,321	10,958
Provision for Loan, Lease, and Other Losses	(150)	(24)
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	2,638	2,750
Financing Receivable, Allowance for Credit Losses, Recovery	1,013	1,298
Financing Receivables Allowance For Credit Losses Net Charge Offs	1,625	1,452
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	11,614	10,553	10,553
Ending balance	11,526	11,091	11,614	10,553
Provision for Loan, Lease, and Other Losses	1,537	1,990
Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	0	0
Financing Receivables Allowance For Credit Losses Net Charge Offs	0	0
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0	0	0
Ending balance	0	0	$ 0	$ 0
Provision for Loan, Lease, and Other Losses	$ 0	$ 0