LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	$ 175,070	$ 208,793	$ 199,422	$ 38,189
Provision for loan losses	(3,984)	26,692	(21,462)	132,188
Loans charged off	(3,537)	(7,371)	(18,249)	(25,370)
Recoveries of loans previously charged off	3,664	3,810	11,502	8,256
Ending balance, Allowance	171,213	231,924	171,213	231,924
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				78,661
Commercial, financial and agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	6,889	7,938	7,359	4,567
Provision for loan losses	(1,471)	5,533	2,606	8,624
Loans charged off	(858)	(1,715)	(6,757)	(4,687)
Recoveries of loans previously charged off	1,986	470	3,338	1,135
Ending balance, Allowance	6,546	12,226	6,546	12,226
Commercial, financial and agricultural \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				2,587
Consumer installment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	7,824	20,085	4,076	3,784
Provision for loan losses	3,063	(3,693)	9,360	5,943
Loans charged off	(1,647)	(677)	(4,764)	(2,781)
Recoveries of loans previously charged off	199	516	767	1,273
Ending balance, Allowance	9,439	16,231	9,439	16,231
Consumer installment \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				8,012
Indirect automobile
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	1,080	3,381	1,929	0
Provision for loan losses	(268)	322	(1,219)	1,138
Loans charged off	(178)	(697)	(1,148)	(2,944)
Recoveries of loans previously charged off	278	317	1,350	1,020
Ending balance, Allowance	912	3,323	912	3,323
Indirect automobile \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				4,109
Mortgage warehouse
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	3,365	1,498	3,666	640
Provision for loan losses	(287)	498	(588)	893
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Ending balance, Allowance	3,078	1,996	3,078	1,996
Mortgage warehouse \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				463
Municipal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	777	507	791	484
Provision for loan losses	(27)	365	(41)	480
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Ending balance, Allowance	750	872	750	872
Municipal \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				(92)
Premium finance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	4,539	8,198	3,879	2,550
Provision for loan losses	(456)	(2,316)	(847)	235
Loans charged off	(605)	(1,159)	(3,142)	(3,893)
Recoveries of loans previously charged off	649	1,224	4,237	2,584
Ending balance, Allowance	4,127	5,947	4,127	5,947
Premium finance \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				4,471
Real estate – construction and development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	18,999	54,266	45,304	5,995
Provision for loan losses	(6,423)	(10,208)	(32,767)	25,379
Loans charged off	0	(9)	(212)	(83)
Recoveries of loans previously charged off	45	182	296	692
Ending balance, Allowance	12,621	44,231	12,621	44,231
Real estate – construction and development \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				12,248
Real estate – commercial and farmland
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	88,338	83,593	88,894	9,666
Provision for loan losses	87	18,419	727	72,410
Loans charged off	(210)	(2,977)	(1,632)	(10,220)
Recoveries of loans previously charged off	266	904	492	1,010
Ending balance, Allowance	88,481	99,939	88,481	99,939
Real estate – commercial and farmland \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				27,073
Real estate – residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	43,259	29,327	43,524	10,503
Provision for loan losses	1,798	17,772	1,307	17,086
Loans charged off	(39)	(137)	(594)	(762)
Recoveries of loans previously charged off	241	197	1,022	542
Ending balance, Allowance	$ 45,259	$ 47,159	$ 45,259	47,159
Real estate – residential \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance				$ 19,790

Amount excluding accrued interest, of allowance for credit loss on financing receivable.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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