LOANS - Loans by Risk Grade (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 12,826,284	$ 8,511,914
Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	7,208,816	5,660,457
Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	5,388,336	2,588,832
1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	533,058	542,164
1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	80,223	90,775
2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	748,511	523,101
2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	108,107	84,617
3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,196,744	2,408,128
3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,660,700	656,289
4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,503,781	2,047,688
4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,242,239	1,586,377
5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	135,179	59,054
5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	117,245	63,613
6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	40,571	35,118
6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	73,664	30,448
7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	50,956	45,204
7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	106,158	76,713
8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	14	0
8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2	0
9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Commercial, financial and agricultural | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,781,237	1,316,359
Commercial, financial and agricultural | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	385,355	372,686
Commercial, financial and agricultural | 1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	520,635	530,864
Commercial, financial and agricultural | 1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	77,581	90,205
Commercial, financial and agricultural | 2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	672,622	452,250
Commercial, financial and agricultural | 2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	18,645	2,648
Commercial, financial and agricultural | 3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	200,075	174,811
Commercial, financial and agricultural | 3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	56,256	20,489
Commercial, financial and agricultural | 4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	360,834	137,038
Commercial, financial and agricultural | 4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	171,329	215,096
Commercial, financial and agricultural | 5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	19,919	13,714
Commercial, financial and agricultural | 5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	32,569	14,445
Commercial, financial and agricultural | 6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,997	5,130
Commercial, financial and agricultural | 6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	8,878	11,601
Commercial, financial and agricultural | 7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	5,141	2,552
Commercial, financial and agricultural | 7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	20,097	18,202
Commercial, financial and agricultural | 8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	14	0
Commercial, financial and agricultural | 8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Commercial, financial and agricultural | 9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Commercial, financial and agricultural | 9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	947,371	671,198
Real estate – construction and development | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	521,324	227,900
Real estate – construction and development | 1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	40
Real estate – construction and development | 1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | 2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	17,908	681
Real estate – construction and development | 2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | 3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	110,267	74,657
Real estate – construction and development | 3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	25,070	18,022
Real estate – construction and development | 4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	780,296	582,456
Real estate – construction and development | 4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	466,461	195,079
Real estate – construction and development | 5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	28,696	6,264
Real estate – construction and development | 5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	9,184	2,728
Real estate – construction and development | 6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	7,531	4,091
Real estate – construction and development | 6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	13,914	1,459
Real estate – construction and development | 7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,673	3,009
Real estate – construction and development | 7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,695	10,612
Real estate – construction and development | 8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | 8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | 9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – construction and development | 9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – commercial and farmland | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,152,528	1,814,529
Real estate – commercial and farmland | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,057,384	1,337,859
Real estate – commercial and farmland | 1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	211	500
Real estate – commercial and farmland | 1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – commercial and farmland | 2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	27,429	37,079
Real estate – commercial and farmland | 2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	9,550	7,407
Real estate – commercial and farmland | 3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,150,753	888,433
Real estate – commercial and farmland | 3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	454,344	230,089
Real estate – commercial and farmland | 4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	843,062	814,068
Real estate – commercial and farmland | 4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,455,604	1,034,943
Real estate – commercial and farmland | 5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	79,753	30,364
Real estate – commercial and farmland | 5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	60,071	29,468
Real estate – commercial and farmland | 6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	27,562	20,959
Real estate – commercial and farmland | 6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	43,747	10,063
Real estate – commercial and farmland | 7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	23,758	23,126
Real estate – commercial and farmland | 7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	34,068	25,889
Real estate – commercial and farmland | 8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – commercial and farmland | 8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – commercial and farmland | 9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – commercial and farmland | 9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – residential | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,866,128	1,403,000
Real estate – residential | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,285,096	623,199
Real estate – residential | 1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	29	16
Real estate – residential | 1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – residential | 2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	30,552	33,043
Real estate – residential | 2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	63,722	74,398
Real estate – residential | 3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,710,512	1,246,383
Real estate – residential | 3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,027,427	385,279
Real estate – residential | 4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	96,029	94,143
Real estate – residential | 4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	129,058	118,082
Real estate – residential | 5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,789	8,634
Real estate – residential | 5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	15,372	16,937
Real estate – residential | 6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	3,378	4,881
Real estate – residential | 6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	6,999	7,231
Real estate – residential | 7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	18,839	15,900
Real estate – residential | 7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	42,518	21,272
Real estate – residential | 8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – residential | 8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – residential | 9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Real estate – residential | 9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Consumer installment | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	461,552	455,371
Consumer installment | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,139,177	27,188
Consumer installment | 1 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	12,183	10,744
Consumer installment | 1 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,642	570
Consumer installment | 2 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	48
Consumer installment | 2 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	16,190	164
Consumer installment | 3 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	25,137	23,844
Consumer installment | 3 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,097,603	2,410
Consumer installment | 4 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	423,560	419,983
Consumer installment | 4 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	19,787	23,177
Consumer installment | 5 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	22	78
Consumer installment | 5 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	49	35
Consumer installment | 6 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	103	57
Consumer installment | 6 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	126	94
Consumer installment | 7 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	545	617
Consumer installment | 7 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,780	738
Consumer installment | 8 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Consumer installment | 8 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	0	0
Consumer installment | 9 | Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2	0
Consumer installment | 9 | Purchased Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 0	$ 0