Loans - Schedule of recorded investment in nonaccrual restructured and loans 90 days past due and accruing (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	$ 90,080	$ 67,954
Restructured Loans	21,298	15,222
Financing Receivable, 90 Days or More Past Due, Still Accruing	2,737	2,302
Financing Receivable Recorded Investment Nonperforming	114,115	85,478
Commercial Financial And Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	26,776	14,998
Restructured Loans	6,349	196
Financing Receivable, 90 Days or More Past Due, Still Accruing	28	10
Financing Receivable Recorded Investment Nonperforming	33,153	15,204
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	39,711	25,566
Restructured Loans	2,080	2,860
Financing Receivable, 90 Days or More Past Due, Still Accruing	625	0
Financing Receivable Recorded Investment Nonperforming	42,416	28,426
Construction Real Estate Remaining Commercial [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	453	1,866
Restructured Loans	0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	453	1,866
Construction Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	25	0
Restructured Loans	84	15
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	20
Financing Receivable Recorded Investment Nonperforming	109	35
Construction Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	72	19
Restructured Loans	5	9
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	77	28
Residential Real Estate Commercial [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	2,025	2,610
Restructured Loans	0	122
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable Recorded Investment Nonperforming	2,025	2,732
Residential Real Estate Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	15,271	16,892
Restructured Loans	8,826	9,100
Financing Receivable, 90 Days or More Past Due, Still Accruing	1,209	1,124
Financing Receivable Recorded Investment Nonperforming	25,306	27,116
Residential Real Estate Home Equity Line Of Credit [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	2,062	2,158
Restructured Loans	1,010	1,028
Financing Receivable, 90 Days or More Past Due, Still Accruing	44	9
Financing Receivable Recorded Investment Nonperforming	3,116	3,195
Residential Real Estate Installment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	462	468
Restructured Loans	1,964	1,049
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	24
Financing Receivable Recorded Investment Nonperforming	2,426	1,541
Consumer Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	3,089	3,377
Restructured Loans	980	843
Financing Receivable, 90 Days or More Past Due, Still Accruing	645	1,115
Financing Receivable Recorded Investment Nonperforming	4,714	5,335
Leases
Financing Receivable, Impaired [Line Items]
Financing Receivable, Nonaccrual	134	0
Restructured Loans	0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	186	0
Financing Receivable Recorded Investment Nonperforming	$ 320	$ 0