LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans Accounted for on a Nonaccrual Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	$ 58,932	$ 76,457
Financing receivable, nonaccrual, no allowance	7,124	13,494
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	5,709	9,836
Financing receivable, nonaccrual, no allowance	221	764
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	462	709
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	1,002	2,831
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	1,564	5,407
Financing receivable, nonaccrual, no allowance	323	416
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	17,459	18,517
Financing receivable, nonaccrual, no allowance	2,815	7,015
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	32,736	39,157
Financing receivable, nonaccrual, no allowance	$ 3,765	$ 5,299