LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 15,874,258	$ 14,480,925	$ 12,818,476
Financing receivable, nonaccrual, no allowance	10,376	13,494
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,875,993	1,627,477	802,171
Financing receivable, nonaccrual, no allowance	164	764
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	191,298	306,995	498,577
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	265,779	580,083	1,061,824
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	787,837	916,353	526,369
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	572,701	659,403	564,304
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	798,409	687,841	654,669
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,452,339	1,606,710	1,549,062
Financing receivable, nonaccrual, no allowance	209	416
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,834,917	5,300,006	4,353,039
Financing receivable, nonaccrual, no allowance	2,061	7,015
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,094,985	2,796,057	$ 2,808,461
Financing receivable, nonaccrual, no allowance	$ 7,942	$ 5,299