LOANS - Loans Receivable, Excluding Purchased Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	$ 4,574,678	$ 3,626,821
Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	4,574,678	3,626,821
Commercial, financial and agricultural | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	1,307,209	967,138
Real estate – construction and development | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	550,189	363,045
Real estate – commercial and farmland | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	1,558,882	1,406,219
Real estate – residential | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	969,289	781,018
Consumer installment | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	183,314	96,915
Other | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable, excluding purchased loans	$ 5,795	$ 12,486