LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans Accounted for on a Nonaccrual Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	$ 59,921	$ 76,457
Financing receivable, nonaccrual, no allowance	11,495	13,494
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	7,284	9,836
Financing receivable, nonaccrual, no allowance	966	764
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	503	709
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	1,393	2,831
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	1,746	5,407
Financing receivable, nonaccrual, no allowance	66	416
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	17,385	18,517
Financing receivable, nonaccrual, no allowance	3,621	7,015
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	31,610	39,157
Financing receivable, nonaccrual, no allowance	$ 6,842	$ 5,299