LOANS - Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 13,094,106	$ 12,818,476	$ 8,482,339
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	827,392	802,171	631,597
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	520,592	498,577	463,105
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	937,736	1,061,824	0
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	547,328	526,369	296,372
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	749,633	564,304	591,302
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	661,845	654,669	487,980
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,628,367	1,549,062	915,976
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,516,451	4,353,039	3,175,452
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 2,704,762	$ 2,808,461	$ 1,920,555