Loans (Recorded Investment By Loan Grade) (Details) - USD ($)		Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment		$ 6,541,548,000	$ 6,520,625,000
Recorded Investment		6,522,519,000	6,501,404,000
Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment		233,049,000	234,463,000
Recorded Investment		232,327,000	233,637,000
Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment		467,189,000	480,420,000
Recorded Investment		466,002,000	479,081,000
Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment	[1]	1,633,043,000	1,614,984,000
Recorded Investment	[1]	1,627,426,000	1,609,413,000
Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment		28,909,000	30,101,000
Recorded Investment		28,892,000	30,081,000
5 Rated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		26,689,000	27,473,000
5 Rated [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		4,857,000	4,857,000
5 Rated [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		549,000	3,839,000
5 Rated [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		11,490,000	11,981,000
5 Rated [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		9,793,000	6,796,000
5 Rated [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		0	0
6 Rated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		212,000	979,000
6 Rated [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment			1,000
6 Rated [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		26,000	30,000
6 Rated [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment			3,000
6 Rated [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		186,000	945,000
6 Rated [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		0	0
Impaired [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		85,863,000	77,528,000
Impaired [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		452,000	453,000
Impaired [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		5,581,000	2,025,000
Impaired [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		29,554,000	33,125,000
Impaired [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		50,147,000	41,791,000
Impaired [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		129,000	134,000
Purchased credit impaired [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		12,912,000	13,469,000
Purchased credit impaired [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		1,032,000	1,044,000
Purchased credit impaired [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		1,583,000	1,754,000
Purchased credit impaired [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		340,000	523,000
Purchased credit impaired [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		620,000	966,000
Purchased credit impaired [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		9,337,000	9,182,000
Pass Rated [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		3,443,948,000	3,430,022,000
Pass Rated [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		226,708,000	228,108,000
Pass Rated [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		459,450,000	472,772,000
Pass Rated [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		1,165,770,000	1,143,428,000
Pass Rated [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		1,563,580,000	1,556,270,000
Pass Rated [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total ending loan balance, recorded investment		28,440,000	29,444,000
Recorded Investment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		3,569,624,000	3,549,471,000
Recorded Investment [Member] | Construction Real Estate Commercial [Domain]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		233,049,000	234,463,000
Recorded Investment [Member] | Residential Real Estate Commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		467,189,000	480,420,000
Recorded Investment [Member] | Commercial, Financial, and Agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		1,207,434,000	1,189,503,000
Recorded Investment [Member] | Commercial Real Estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		1,633,043,000	1,614,984,000
Recorded Investment [Member] | Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment		$ 28,909,000	30,101,000
Financial Asset Acquired with Credit Deterioration [Member] | Nonperforming Financial Instruments [Member] | Purchased credit impaired [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and Leases Receivable, Recorded Investment			6,000
Total ending loan balance, recorded investment			$ 5,000

[1] 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.