Loans - Schedule of recorded investment in nonaccrual restructured and loans 90 days past due and accruing (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	$ 117,368	$ 90,080
Restructured Loans	20,888	21,298
Financing Receivable, 90 Days or More Past Due, Still Accruing	1,594	2,737
Financing Receivable Recorded Investment Nonperforming	139,850	114,115
Commercial Financial And Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	23,261	26,776
Restructured Loans	5,619	6,349
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	28
Financing Receivable Recorded Investment Nonperforming	28,880	33,153
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	67,426	39,711
Restructured Loans	2,931	2,080
Financing Receivable, 90 Days or More Past Due, Still Accruing	377	625
Financing Receivable Recorded Investment Nonperforming	70,734	42,416
Construction Real Estate Remaining Commercial [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	3,110	453
Restructured Loans	0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	3,110	453
Construction Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	0	25
Restructured Loans	30	84
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	30	109
Construction Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	14	72
Restructured Loans	1	5
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	15	77
Residential Real Estate Commercial [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	4,304	2,025
Restructured Loans	253	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	4,557	2,025
Residential Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	14,016	15,271
Restructured Loans	8,400	8,826
Financing Receivable, 90 Days or More Past Due, Still Accruing	416	1,209
Financing Receivable Recorded Investment Nonperforming	22,832	25,306
Residential Real Estate Home Equity Line Of Credit [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	1,286	2,062
Restructured Loans	909	1,010
Financing Receivable, 90 Days or More Past Due, Still Accruing	77	44
Financing Receivable Recorded Investment Nonperforming	2,272	3,116
Residential Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	184	462
Restructured Loans	1,728	1,964
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	1,912	2,426
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	2,172	3,089
Restructured Loans	1,017	980
Financing Receivable, 90 Days or More Past Due, Still Accruing	724	645
Financing Receivable Recorded Investment Nonperforming	3,913	4,714
Leases
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	1,595	134
Restructured Loans	0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	186
Financing Receivable Recorded Investment Nonperforming	$ 1,595	$ 320