LOANS - Loans Receivable, Excluding Purchased Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 8,529,518	$ 6,046,355
Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	5,543,306	4,856,514
Commercial, financial and agricultural | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,422,152	1,362,508
Real estate – construction and development | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	641,830	624,595
Real estate – commercial and farmland | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,804,265	1,535,439
Real estate – residential | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,275,201	1,009,461
Consumer installment | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 399,858	$ 324,511