LOANS - Purchased Loans (Details) - Purchased Loans - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 2,711,460	$ 861,595
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	413,365	74,378
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	219,882	65,513
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,399,174	468,246
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	649,352	250,539
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 29,687	$ 2,919