Allowance for Loan Losses Activity in the allowance for loan losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 85,675	$ 56,679	$ 51,512	$ 49,988
Financing Receivable, Allowance for Credit Losses, Write-downs	10,304	11,177	13,552
Financing Receivable, Allowance for Credit Losses, Recovery	27,246	10,173	7,131
Financing Receivables Allowance For Credit Losses Net Charge Offs	(16,942)	1,004	6,421
Provision for Loan, Lease, and Other Losses	12,054	6,171	7,945
Commercial Financial And Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	25,608	20,203	16,777	15,022
Financing Receivable, Allowance for Credit Losses, Write-downs	1,468	2,231	2,796
Financing Receivable, Allowance for Credit Losses, Recovery	20,765	1,241	1,221
Financing Receivables Allowance For Credit Losses Net Charge Offs	(19,297)	990	1,575
Provision for Loan, Lease, and Other Losses	(13,892)	4,416	3,330
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	23,480	10,229	9,768	9,601
Financing Receivable, Allowance for Credit Losses, Write-downs	1,824	400	281
Financing Receivable, Allowance for Credit Losses, Recovery	738	720	272
Financing Receivables Allowance For Credit Losses Net Charge Offs	1,086	(320)	9
Provision for Loan, Lease, and Other Losses	14,337	141	176
Construction Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	7,288	5,311	4,463	4,430
Financing Receivable, Allowance for Credit Losses, Write-downs	6	0	72
Financing Receivable, Allowance for Credit Losses, Recovery	1,122	2,682	712
Financing Receivables Allowance For Credit Losses Net Charge Offs	(1,116)	(2,682)	(640)
Provision for Loan, Lease, and Other Losses	861	(1,834)	(607)
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	11,363	8,610	8,731	9,321
Financing Receivable, Allowance for Credit Losses, Write-downs	356	239	441
Financing Receivable, Allowance for Credit Losses, Recovery	991	787	844
Financing Receivables Allowance For Credit Losses Net Charge Offs	(635)	(548)	(403)
Provision for Loan, Lease, and Other Losses	2,118	(669)	(993)
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	17,418	12,211	11,773	11,614
Financing Receivable, Allowance for Credit Losses, Write-downs	6,634	8,307	9,962
Financing Receivable, Allowance for Credit Losses, Recovery	3,629	4,742	4,078
Financing Receivables Allowance For Credit Losses Net Charge Offs	3,005	3,565	5,884
Provision for Loan, Lease, and Other Losses	8,212	4,003	6,043
Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	518	115	0	$ 0
Financing Receivable, Allowance for Credit Losses, Write-downs	16	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	1	1	4
Financing Receivables Allowance For Credit Losses Net Charge Offs	15	(1)	(4)
Provision for Loan, Lease, and Other Losses	$ 418	$ 114	$ (4)