LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans by Class Modified as Troubled Debt Restructurings (Details) - Loans Excluding Purchased Loan $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($) contract branch	Jun. 30, 2020 USD ($) contract branch	Jun. 30, 2021 USD ($) contract branch	Jun. 30, 2020 USD ($) contract branch	Dec. 31, 2020 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	9	9	25	83
Troubled debt restructurings principal balances	$ 9,298	$ 1,577	$ 18,368	$ 11,278
Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	25	7	60	16
Troubled debt restructurings principal balances	$ 1,169	$ 168	$ 7,195	$ 1,732
Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			628		752
Troubled debt restructurings principal balances			$ 81,206		$ 78,843
Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			122		128
Troubled debt restructurings principal balances			$ 11,068		$ 6,145
Commercial, financial and agricultural
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	2	1	6	1
Troubled debt restructurings principal balances	$ 165	$ 731	$ 591	$ 731
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0	3	1
Troubled debt restructurings principal balances	$ 0	$ 0	$ 49	$ 200
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			12		9
Troubled debt restructurings principal balances			$ 1,038		$ 521
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			10		11
Troubled debt restructurings principal balances			$ 805		$ 849
Consumer installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	2	3	2	4
Troubled debt restructurings principal balances	$ 8	$ 7	$ 8	$ 15
Consumer installment | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	3	4	3
Troubled debt restructurings principal balances	$ 0	$ 4	$ 5	$ 4
Consumer installment | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			9		10
Troubled debt restructurings principal balances			$ 28		$ 32
Consumer installment | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			19		20
Troubled debt restructurings principal balances			$ 43		$ 56
Indirect automobile | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | branch	7	0	22	0
Troubled debt restructurings principal balances	$ 27	$ 0	$ 112	$ 0
Indirect automobile | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			336		437
Troubled debt restructurings principal balances			$ 1,647		$ 2,277
Indirect automobile | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			47		51
Troubled debt restructurings principal balances			$ 301		$ 461
Real estate – construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0	0	1
Troubled debt restructurings principal balances	$ 0	$ 0	$ 0	$ 20
Real estate – construction and development | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	0	1	2
Troubled debt restructurings principal balances	$ 0	$ 0	$ 1	$ 285
Real estate – construction and development | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			5		4
Troubled debt restructurings principal balances			$ 898		$ 506
Real estate – construction and development | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			4		5
Troubled debt restructurings principal balances			$ 301		$ 707
Real estate – commercial and farmland
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	3	0	5	1
Troubled debt restructurings principal balances	$ 8,653	$ 0	$ 16,312	$ 16
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	1	0	3	2
Troubled debt restructurings principal balances	$ 202	$ 0	$ 5,382	$ 676
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			28		28
Troubled debt restructurings principal balances			$ 46,025		$ 36,707
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			11		7
Troubled debt restructurings principal balances			$ 7,103		$ 1,401
Real estate – residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	2	5	12	76
Troubled debt restructurings principal balances	$ 472	$ 839	$ 1,457	$ 10,496
Real estate – residential | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	17	4	27	8
Troubled debt restructurings principal balances	$ 940	$ 164	$ 1,646	$ 567
Real estate – residential | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			238		264
Troubled debt restructurings principal balances			$ 31,570		$ 38,800
Real estate – residential | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract			31		34
Troubled debt restructurings principal balances			$ 2,515		$ 2,671