LOANS - Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 14,599,805	$ 14,480,925
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,611,029	1,627,477
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	257,097	306,995
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	482,637	580,083
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	880,216	916,353
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	659,228	659,403
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	706,379	687,841
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,533,234	1,606,710
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	5,616,826	5,300,006
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 2,853,159	$ 2,796,057