LOANS - Loans Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 14,503,157	$ 12,818,476	$ 9,049,870
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,839,921	802,171	703,290
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	575,782	498,577	474,195
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	739,543	1,061,824
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	748,853	526,369	462,481
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	731,508	564,304	583,558
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	690,584	654,669	613,964
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,641,744	1,549,062	1,103,550
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,804,420	4,353,039	3,182,213
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 2,730,802	$ 2,808,461	$ 1,926,619