LOANS AND ALLOWANCE FOR LOAN LOSSES - Loans Receivable, Excluding Purchased Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 6,046,355	$ 5,264,326
Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	4,856,514	3,626,821
Commercial, financial and agricultural | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,362,508	967,138
Real estate – construction and development | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	624,595	363,045
Real estate – commercial and farmland | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,535,439	1,406,219
Real estate – residential | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,009,461	781,018
Consumer installment | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	309,194	96,915
Other | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 15,317	$ 12,486