LOANS AND ALLOWANCE FOR CREDIT LOSSES - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, Allowance	$ 178,570	$ 149,524	$ 199,422	$ 38,189
Provision for loan losses	(899)	68,449	(17,478)	105,496
Loans charged off	(7,138)	(11,281)	(14,712)	(17,999)
Recoveries of loans previously charged off	4,537	2,101	7,838	4,446
Ending balance, Allowance	175,070	208,793	175,070	208,793
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	8,291	8,110	7,359	4,567
Provision for loan losses	1,502	11	4,077	3,091
Loans charged off	(3,529)	(486)	(5,899)	(2,972)
Recoveries of loans previously charged off	625	303	1,352	665
Ending balance, Allowance	6,889	7,938	6,889	7,938
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	8,790	15,446	4,076	3,784
Provision for loan losses	491	5,165	6,297	9,636
Loans charged off	(1,669)	(962)	(3,117)	(2,104)
Recoveries of loans previously charged off	212	436	568	757
Ending balance, Allowance	7,824	20,085	7,824	20,085
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	1,272	3,464	1,929	0
Provision for loan losses	(423)	574	(951)	816
Loans charged off	(141)	(1,016)	(970)	(2,247)
Recoveries of loans previously charged off	372	359	1,072	703
Ending balance, Allowance	1,080	3,381	1,080	3,381
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	3,521	1,102	3,666	640
Provision for loan losses	(156)	396	(301)	395
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Ending balance, Allowance	3,365	1,498	3,365	1,498
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	790	522	791	484
Provision for loan losses	(13)	(15)	(14)	115
Loans charged off	0	0	0	0
Recoveries of loans previously charged off	0	0	0	0
Ending balance, Allowance	777	507	777	507
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	4,100	11,508	3,879	2,550
Provision for loan losses	(833)	(2,083)	(391)	2,551
Loans charged off	(1,194)	(1,903)	(2,537)	(2,734)
Recoveries of loans previously charged off	2,466	676	3,588	1,360
Ending balance, Allowance	4,539	8,198	4,539	8,198
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	22,858	25,319	45,304	5,995
Provision for loan losses	(3,757)	28,853	(26,344)	35,587
Loans charged off	(186)	(74)	(212)	(74)
Recoveries of loans previously charged off	84	168	251	510
Ending balance, Allowance	18,999	54,266	18,999	54,266
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	91,211	51,754	88,894	9,666
Provision for loan losses	(3,031)	38,133	640	53,991
Loans charged off	(27)	(6,315)	(1,422)	(7,243)
Recoveries of loans previously charged off	185	21	226	106
Ending balance, Allowance	88,338	83,593	88,338	83,593
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	37,737	32,299	43,524	10,503
Provision for loan losses	5,321	(2,585)	(491)	(686)
Loans charged off	(392)	(525)	(555)	(625)
Recoveries of loans previously charged off	593	138	781	345
Ending balance, Allowance	$ 43,259	$ 29,327	$ 43,259	29,327
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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