LOANS - Analysis of Past-Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	$ 134,707	$ 134,659
Current Loans	14,465,098	14,346,266
Total Loans	14,599,805	14,480,925
Loans 90 Days or More Past Due and Still Accruing	5,097	8,326
Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	65,104	56,483
Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	11,886	13,582
Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	57,717	64,594
Commercial, financial and agricultural
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	11,745	12,246
Current Loans	1,599,284	1,615,231
Total Loans	1,611,029	1,627,477
Loans 90 Days or More Past Due and Still Accruing	0	0
Commercial, financial and agricultural | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	5,729	4,576
Commercial, financial and agricultural | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,094	2,018
Commercial, financial and agricultural | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	4,922	5,652
Consumer installment
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	3,919	5,621
Current Loans	253,178	301,374
Total Loans	257,097	306,995
Loans 90 Days or More Past Due and Still Accruing	749	1,755
Consumer installment | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,774	2,189
Consumer installment | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,017	1,114
Consumer installment | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,128	2,318
Indirect automobile
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	2,325	6,470
Current Loans	480,312	573,613
Total Loans	482,637	580,083
Loans 90 Days or More Past Due and Still Accruing	0	0
Indirect automobile | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,036	3,293
Indirect automobile | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	318	1,006
Indirect automobile | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	971	2,171
Mortgage warehouse
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Current Loans	880,216	916,353
Total Loans	880,216	916,353
Loans 90 Days or More Past Due and Still Accruing	0	0
Mortgage warehouse | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Mortgage warehouse | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Mortgage warehouse | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Municipal
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Current Loans	659,228	659,403
Total Loans	659,228	659,403
Loans 90 Days or More Past Due and Still Accruing	0	0
Municipal | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Municipal | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Municipal | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	0	0
Premium finance
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	11,583	17,654
Current Loans	694,796	670,187
Total Loans	706,379	687,841
Loans 90 Days or More Past Due and Still Accruing	4,057	6,571
Premium finance | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	4,693	7,188
Premium finance | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	2,833	3,895
Premium finance | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	4,057	6,571
Real estate – construction and development
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	33,288	19,221
Current Loans	1,499,946	1,587,489
Total Loans	1,533,234	1,606,710
Loans 90 Days or More Past Due and Still Accruing	291	0
Real estate – construction and development | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	28,769	13,348
Real estate – construction and development | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	1,898	723
Real estate – construction and development | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	2,621	5,150
Real estate – commercial and farmland
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	18,437	15,722
Current Loans	5,598,389	5,284,284
Total Loans	5,616,826	5,300,006
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – commercial and farmland | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	9,796	5,370
Real estate – commercial and farmland | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	527	1,701
Real estate – commercial and farmland | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	8,114	8,651
Real estate – residential
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	53,410	57,725
Current Loans	2,799,749	2,738,332
Total Loans	2,853,159	2,796,057
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – residential | Loans 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	13,307	20,519
Real estate – residential | Loans 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	4,199	3,125
Real estate – residential | Loans 90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Past Due	$ 35,904	$ 34,081