LOANS AND ALLOWANCE FOR CREDIT LOSSES - Loans by Risk Grade (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 14,824,539	$ 14,480,925
9
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	528,345	1,034,506
Year two	160,151	138,136
Year three	103,388	100,900
Year four	78,569	68,339
Year five	45,092	28,655
Prior	48,989	45,190
Revolving Loans Amortized Cost Basis	253,041	211,751
Loans, net of unearned income	1,217,575	1,627,477
Commercial, financial and agricultural | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	527,587	1,031,173
Year two	158,865	134,604
Year three	99,010	97,815
Year four	75,973	64,573
Year five	42,009	23,852
Prior	40,557	38,744
Revolving Loans Amortized Cost Basis	244,459	209,214
Loans, net of unearned income	1,188,460	1,599,975
Commercial, financial and agricultural | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	36	21
Year two	776	72
Year three	527	506
Year four	445	193
Year five	439	3,509
Prior	3,381	1,232
Revolving Loans Amortized Cost Basis	1,439	632
Loans, net of unearned income	7,043	6,165
Commercial, financial and agricultural | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	722	3,312
Year two	510	3,460
Year three	3,851	2,579
Year four	2,151	3,573
Year five	2,644	1,294
Prior	5,051	5,214
Revolving Loans Amortized Cost Basis	7,143	1,886
Loans, net of unearned income	22,072	21,318
Commercial, financial and agricultural | 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one		0
Year two		0
Year three		0
Year four		0
Year five		0
Prior		0
Revolving Loans Amortized Cost Basis		19
Loans, net of unearned income		19
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	32,110	142,833
Year two	70,119	63,892
Year three	42,462	57,725
Year four	30,845	17,936
Year five	11,492	4,808
Prior	12,462	11,042
Revolving Loans Amortized Cost Basis	7,621	8,759
Loans, net of unearned income	207,111	306,995
Consumer installment | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	32,105	142,803
Year two	69,866	63,681
Year three	42,133	57,644
Year four	30,626	17,831
Year five	11,439	4,674
Prior	11,851	10,344
Revolving Loans Amortized Cost Basis	7,532	8,662
Loans, net of unearned income	205,552	305,639
Consumer installment | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	2
Year three	0	9
Year four	0	0
Year five	0	0
Prior	138	145
Revolving Loans Amortized Cost Basis	6	0
Loans, net of unearned income	144	156
Consumer installment | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	5	30
Year two	253	209
Year three	329	72
Year four	219	105
Year five	53	134
Prior	473	553
Revolving Loans Amortized Cost Basis	83	97
Loans, net of unearned income	1,415	1,200
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	35,595
Year three	23,839	188,313
Year four	118,997	188,964
Year five	110,460	110,066
Prior	71,761	57,145
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	325,057	580,083
Indirect automobile | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	35,432
Year three	23,803	187,737
Year four	118,811	188,333
Year five	110,168	108,926
Prior	70,808	55,835
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	323,590	576,263
Indirect automobile | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	57
Year four	27	70
Year five	28	62
Prior	66	85
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	121	274
Indirect automobile | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	163
Year three	36	519
Year four	159	561
Year five	264	1,078
Prior	887	1,225
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	1,346	3,546
Mortgage warehouse
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	768,577	916,353
Loans, net of unearned income	768,577	916,353
Mortgage warehouse | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	768,577	916,353
Loans, net of unearned income	768,577	916,353
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	42,565	236,076
Year two	227,256	13,398
Year three	14,911	8,944
Year four	5,753	149,194
Year five	141,822	141,543
Prior	192,123	110,248
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	624,430	659,403
Municipal | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	42,565	236,076
Year two	227,256	13,398
Year three	14,911	8,944
Year four	5,753	149,194
Year five	141,822	141,543
Prior	192,123	110,248
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	624,430	659,403
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	824,425	667,425
Year two	15,709	18,996
Year three	176	515
Year four	0	746
Year five	414	121
Prior	13	38
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	840,737	687,841
Premium finance | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	820,843	661,614
Year two	13,411	18,236
Year three	175	515
Year four	0	746
Year five	414	121
Prior	13	38
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	834,856	681,270
Premium finance | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	3,582	5,811
Year two	2,298	760
Year three	1	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	5,881	6,571
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	630,507	666,893
Year two	411,824	483,145
Year three	234,909	226,138
Year four	58,198	73,061
Year five	40,095	35,841
Prior	52,267	51,658
Revolving Loans Amortized Cost Basis	27,024	69,974
Loans, net of unearned income	1,454,824	1,606,710
Real estate – construction and development | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	629,733	666,193
Year two	411,682	479,251
Year three	234,740	221,926
Year four	55,995	71,488
Year five	39,464	35,799
Prior	49,180	43,958
Revolving Loans Amortized Cost Basis	27,024	69,974
Loans, net of unearned income	1,447,818	1,588,589
Real estate – construction and development | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	685
Year two	0	1,036
Year three	0	3,646
Year four	0	1,302
Year five	0	0
Prior	1,853	4,564
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	1,853	11,233
Real estate – construction and development | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	774	15
Year two	142	2,858
Year three	169	566
Year four	2,203	271
Year five	631	42
Prior	1,234	3,136
Revolving Loans Amortized Cost Basis	0	0
Loans, net of unearned income	5,153	6,888
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	1,473,720	1,275,475
Year two	1,257,318	1,060,392
Year three	1,135,440	660,156
Year four	625,725	655,451
Year five	548,966	531,935
Prior	1,281,410	1,012,521
Revolving Loans Amortized Cost Basis	87,125	104,076
Loans, net of unearned income	6,409,704	5,300,006
Real estate – commercial and farmland | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	1,471,281	1,275,225
Year two	1,254,639	995,273
Year three	1,118,208	636,687
Year four	592,121	611,823
Year five	522,226	497,221
Prior	1,208,209	925,534
Revolving Loans Amortized Cost Basis	85,462	103,805
Loans, net of unearned income	6,252,146	5,045,568
Real estate – commercial and farmland | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	462	0
Year two	0	10,680
Year three	6,317	4,895
Year four	14,835	28,139
Year five	21,200	7,670
Prior	26,354	31,224
Revolving Loans Amortized Cost Basis	1,640	0
Loans, net of unearned income	70,808	82,608
Real estate – commercial and farmland | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	1,977	250
Year two	2,679	54,439
Year three	10,915	18,574
Year four	18,769	15,489
Year five	5,540	27,044
Prior	46,847	55,763
Revolving Loans Amortized Cost Basis	23	271
Loans, net of unearned income	86,750	171,830
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	892,752	786,803
Year two	699,143	562,538
Year three	383,314	287,286
Year four	179,254	206,739
Year five	125,944	173,832
Prior	475,725	522,873
Revolving Loans Amortized Cost Basis	220,392	255,986
Loans, net of unearned income	2,976,524	2,796,057
Real estate – residential | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	891,155	782,834
Year two	691,763	551,308
Year three	367,862	273,917
Year four	169,881	201,738
Year five	121,410	170,951
Prior	456,393	502,823
Revolving Loans Amortized Cost Basis	218,163	252,787
Loans, net of unearned income	2,916,627	2,736,358
Real estate – residential | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	806	527
Year two	67	1,843
Year three	1,156	1,030
Year four	586	334
Year five	445	724
Prior	4,590	3,391
Revolving Loans Amortized Cost Basis	139	255
Loans, net of unearned income	7,789	8,104
Real estate – residential | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	791	3,442
Year two	7,313	9,387
Year three	14,296	12,339
Year four	8,787	4,667
Year five	4,089	2,157
Prior	14,742	16,659
Revolving Loans Amortized Cost Basis	2,090	2,944
Loans, net of unearned income	$ 52,108	$ 51,595