LOANS AND ALLOWANCE FOR CREDIT LOSSES - Deferrals Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 76,525	$ 332,779
Deferrals as a % of total loans	0.50%	2.30%
Commercial, financial and agricultural
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 755	$ 12,471
Deferrals as a % of total loans	0.10%	0.80%
Consumer installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 0	$ 1,418
Deferrals as a % of total loans	0.00%	0.50%
Indirect automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 1,302	$ 8,936
Deferrals as a % of total loans	0.40%	1.50%
Real estate – construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 0	$ 11,049
Deferrals as a % of total loans	0.00%	0.70%
Real estate – commercial and farmland
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 26,128	$ 179,183
Deferrals as a % of total loans	0.40%	3.40%
Real estate – residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 48,340	$ 119,722
Deferrals as a % of total loans	1.60%	4.30%