LOANS AND ALLOWANCE FOR CREDIT LOSSES - Deferrals Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 127,725	$ 332,779
Deferrals as a % of total loans	0.90%	2.30%
Commercial, financial and agricultural
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 2,539	$ 12,471
Deferrals as a % of total loans	0.20%	0.80%
Consumer installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 29	$ 1,418
Deferrals as a % of total loans	0.00%	0.50%
Indirect automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 1,126	$ 8,936
Deferrals as a % of total loans	0.30%	1.50%
Real estate – construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 873	$ 11,049
Deferrals as a % of total loans	0.10%	0.70%
Real estate – commercial and farmland
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 63,827	$ 179,183
Deferrals as a % of total loans	1.10%	3.40%
Real estate – residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
COVID-19 Deferrals	$ 59,331	$ 119,722
Deferrals as a % of total loans	2.00%	4.30%