LOANS AND ALLOWANCE FOR LOAN LOSSES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual, interest income	$ 0
Balance	123,082,000
Nonaccrual loans	76,457,000	$ 75,124,000
Loans modified that are not troubled debt restructurings	436,000,000.0	325,700,000
Troubled debt restructurings excluding purchased loans	85,000,000.0	35,200,000
Troubled debt restructurings, previous charge-offs	1,200,000	1,900,000
COVID-19 Deferrals	332,779,000
Loans charged off	54,464,000	19,861,000	$ 21,131,000
Loans held for sale	1,167,659,000	1,656,711,000
Release of provision for loan losses	(125,488,000)	(19,758,000)	(16,667,000)
Loans, net of unearned income	14,480,925,000	12,818,476,000	8,511,914,000
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance	100,180,000
Nonaccrual loans	18,517,000	23,797,000
COVID-19 Deferrals	179,183,000
Loans charged off	27,504,000	3,342,000	356,000
Release of provision for loan losses	(78,210,000)	(3,017,000)	(855,000)
Loans, net of unearned income	5,300,006,000	4,353,039,000	3,152,388,000
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	709,000	831,000
COVID-19 Deferrals	1,418,000
Loans charged off	5,642,000	5,899,000	4,414,000
Release of provision for loan losses	3,831,000	(4,268,000)	(5,468,000)
Loans, net of unearned income	306,995,000	498,577,000	482,559,000
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance	5,490,000
Nonaccrual loans	9,836,000	9,236,000
COVID-19 Deferrals	12,471,000
Loans charged off	10,647,000	3,460,000	1,908,000
Release of provision for loan losses	(8,963,000)	(3,837,000)	117,000
Loans, net of unearned income	1,627,477,000	802,171,000	680,720,000
Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	49,381,000	8,504,000
Allowance for loan losses allocated to troubled debt restructurings	13,000,000.0	3,700,000
Loans Excluding Purchased Loan | Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	31,630,000	220,000
Loans Excluding Purchased Loan | Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	15,000	58,000
Loans Excluding Purchased Loan | Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	855,000	627,000
Loans Excluding Purchased Loan | Financing Receivables, 1 to 29 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	4,378,000	4,193,000
Loans Excluding Purchased Loan | Financing Receivables, 1 to 29 Days Past Due | Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	929,000	1,942,000
Loans Excluding Purchased Loan | Financing Receivables, 1 to 29 Days Past Due | Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	2,000	32,000
Loans Excluding Purchased Loan | Financing Receivables, 1 to 29 Days Past Due | Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructuring loans	2,000	87,000
Hotel Loans | Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of loans	87,500,000
Loans charged off	17,200,000
Loss on sale of loans	386,000
Held For Sale Loans | Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans charged off	1,600,000
Loans held for sale	165,900,000
Release of provision for loan losses	6,700,000
PPP Loans | Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	827,400,000
Minimum | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	100,000	100,000	100,000
Troubled debt restructuring loans	$ 100,000	$ 100,000	$ 100,000