Allowance for Loan Losses Composition (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	$ 5,230,000	$ 2,273,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	51,181,000	49,239,000
Acquired with deteriorated credit quality	268,000	0
Financing Receivable, Allowance for Credit Losses	56,679,000	51,512,000
Financing Receivable, Individually Evaluated for Impairment	77,459,000	48,135,000
Financing Receivable, Collectively Evaluated for Impairment	6,409,614,000	5,640,054,000
Loans acquired with deteriorated credit quality (1)	14,331,000	3,943,000
Loans and Leases Receivable, Net of Deferred Income	$ 6,501,404,000	$ 5,692,132,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	6.75%	4.72%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	0.80%	0.87%
Loans acquired with deteriorated credit quality	1.87%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	0.87%	0.90%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 77,491,000	$ 48,144,000
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	6,428,693,000	5,657,693,000
Loans acquired with deteriorated credit quality (1)	14,441,000	3,961,000
Loans and Leases Receivable, Recorded Investment	6,520,625,000	5,709,798,000
Total loans	6,501,404,000	5,692,132,000	$ 5,372,483,000
Purchased credit impaired [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,469,000	3,961,000
Commercial Financial And Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	5,104,000	2,169,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	14,948,000	14,608,000
Acquired with deteriorated credit quality	151,000	0
Financing Receivable, Allowance for Credit Losses	20,203,000	16,777,000
Financing Receivable, Individually Evaluated for Impairment	33,077,000	15,119,000
Financing Receivable, Collectively Evaluated for Impairment	1,151,073,000	1,057,520,000
Loans acquired with deteriorated credit quality (1)	960,000	147,000
Loans and Leases Receivable, Net of Deferred Income	$ 1,185,110,000	$ 1,072,786,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	15.43%	14.35%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	1.30%	1.38%
Loans acquired with deteriorated credit quality	15.73%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	1.70%	1.56%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 33,088,000	$ 15,120,000
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	1,155,449,000	1,062,121,000
Loans acquired with deteriorated credit quality (1)	966,000	148,000
Loans and Leases Receivable, Recorded Investment	1,189,503,000	1,077,389,000
Commercial Financial And Agricultural [Member] | Purchased credit impaired [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	966,000	148,000
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	35,000	86,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	10,187,000	9,682,000
Acquired with deteriorated credit quality	7,000	0
Financing Receivable, Allowance for Credit Losses	10,229,000	9,768,000
Financing Receivable, Individually Evaluated for Impairment	41,770,000	28,418,000
Financing Receivable, Collectively Evaluated for Impairment	1,558,550,000	1,251,579,000
Loans acquired with deteriorated credit quality (1)	9,093,000	3,048,000
Loans and Leases Receivable, Net of Deferred Income	$ 1,609,413,000	$ 1,283,045,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	0.08%	0.30%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	0.65%	0.77%
Loans acquired with deteriorated credit quality	0.08%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	0.64%	0.76%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 41,791,000	$ 28,426,000
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	1,564,011,000	1,256,310,000
Loans acquired with deteriorated credit quality (1)	9,182,000	3,059,000
Loans and Leases Receivable, Recorded Investment	1,614,984,000	1,287,795,000
Commercial Real Estate Portfolio Segment [Member] | Purchased credit impaired [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,182,000	3,059,000
Construction Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,311,000	4,463,000
Acquired with deteriorated credit quality	0	0
Financing Receivable, Allowance for Credit Losses	5,311,000	4,463,000
Financing Receivable, Individually Evaluated for Impairment	453,000	1,866,000
Financing Receivable, Collectively Evaluated for Impairment	330,106,000	245,909,000
Loans acquired with deteriorated credit quality (1)	1,140,000	499,000
Loans and Leases Receivable, Net of Deferred Income	$ 331,699,000	$ 248,274,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	0.00%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	1.61%	1.81%
Loans acquired with deteriorated credit quality	0.00%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	1.60%	1.80%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 453,000	$ 1,866,000
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	331,161,000	246,864,000
Loans acquired with deteriorated credit quality (1)	1,143,000	503,000
Loans and Leases Receivable, Recorded Investment	332,757,000	249,233,000
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	42,000	18,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	8,458,000	8,713,000
Acquired with deteriorated credit quality	110,000	0
Financing Receivable, Allowance for Credit Losses	8,610,000	8,731,000
Financing Receivable, Individually Evaluated for Impairment	2,025,000	2,732,000
Financing Receivable, Collectively Evaluated for Impairment	1,888,088,000	1,790,637,000
Loans acquired with deteriorated credit quality (1)	2,613,000	249,000
Loans and Leases Receivable, Net of Deferred Income	$ 1,892,726,000	$ 1,793,618,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	2.07%	0.66%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	0.45%	0.49%
Loans acquired with deteriorated credit quality	4.21%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	0.45%	0.49%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 2,025,000	$ 2,732,000
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	1,891,941,000	1,794,207,000
Loans acquired with deteriorated credit quality (1)	2,625,000	251,000
Loans and Leases Receivable, Recorded Investment	1,896,591,000	1,797,190,000
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	12,211,000	11,773,000
Acquired with deteriorated credit quality	0	0
Financing Receivable, Allowance for Credit Losses	12,211,000	11,773,000
Financing Receivable, Individually Evaluated for Impairment	0	0
Financing Receivable, Collectively Evaluated for Impairment	1,452,373,000	1,292,136,000
Loans acquired with deteriorated credit quality (1)	2,000	0
Loans and Leases Receivable, Net of Deferred Income	$ 1,452,375,000	$ 1,292,136,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	0.00%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	0.84%	0.91%
Loans acquired with deteriorated credit quality	0.00%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	0.84%	0.91%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 0	$ 0
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	1,456,687,000	1,295,892,000
Loans acquired with deteriorated credit quality (1)	2,000	0
Loans and Leases Receivable, Recorded Investment	1,456,689,000	1,295,892,000
Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	49,000	0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	66,000	0
Acquired with deteriorated credit quality	0	0
Financing Receivable, Allowance for Credit Losses	115,000	0
Financing Receivable, Individually Evaluated for Impairment	134,000	0
Financing Receivable, Collectively Evaluated for Impairment	29,424,000	2,273,000
Loans acquired with deteriorated credit quality (1)	523,000	0
Loans and Leases Receivable, Net of Deferred Income	$ 30,081,000	$ 2,273,000
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Individually Evaluated for Impairment	36.57%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans, Collectively Evaluated for Impairment	0.22%	0.00%
Loans acquired with deteriorated credit quality	0.00%	0.00%
Loans And Leases Receivable, Ratio Of Allowance For Loan Losses To Total Loans	0.38%	0.00%
Loans And Leases Receivable, Recorded Investment, Individually Evaluated for Impairment	$ 134,000	$ 0
Loans And Leases Receivable, Recorded Investment, Collectively Evaluated for Impairment	29,444,000	2,299,000
Loans acquired with deteriorated credit quality (1)	523,000	0
Loans and Leases Receivable, Recorded Investment	30,101,000	2,299,000
Leases | Purchased credit impaired [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	523,000	0
Commercial Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Nonperforming Financial Instruments [Member] | Purchased credit impaired [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Loans and Leases Receivable, Recorded Investment	6,000	475,000
Total loans	$ 5,000	$ 475,000