LOANS - Analysis of Past-Due Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 8,529,518	$ 6,046,355
Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	35,856	44,215
Current Loans	5,507,450	4,812,299
Total Loans	5,543,306	4,856,514
Loans 90 Days or More Past Due and Still Accruing	2,863	5,991
Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	14,671	20,131
Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	6,330	7,508
Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	14,855	16,576
Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	37,483	14,774
Current Loans	2,673,977	846,821
Total Loans	2,711,460	861,595
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	14,361	4,056
Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	4,415	2,354
Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	18,707	8,364
Commercial, financial and agricultural | Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	12,443	18,387
Current Loans	1,409,709	1,344,121
Total Loans	1,422,152	1,362,508
Loans 90 Days or More Past Due and Still Accruing	2,657	5,991
Commercial, financial and agricultural | Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	6,085	8,124
Commercial, financial and agricultural | Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,484	3,285
Commercial, financial and agricultural | Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	3,874	6,978
Commercial, financial and agricultural | Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,144	793
Current Loans	412,221	73,585
Total Loans	413,365	74,378
Loans 90 Days or More Past Due and Still Accruing	0	0
Commercial, financial and agricultural | Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	320	0
Commercial, financial and agricultural | Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	131	33
Commercial, financial and agricultural | Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	693	760
Real estate – construction and development | Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,349	1,121
Current Loans	640,481	623,474
Total Loans	641,830	624,595
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – construction and development | Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	376	810
Real estate – construction and development | Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	129	23
Real estate – construction and development | Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	844	288
Real estate – construction and development | Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	6,085	2,635
Current Loans	213,797	62,878
Total Loans	219,882	65,513
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – construction and development | Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	398	87
Real estate – construction and development | Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	407	31
Real estate – construction and development | Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	5,280	2,517
Real estate – commercial and farmland | Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	4,516	3,596
Current Loans	1,799,749	1,531,843
Total Loans	1,804,265	1,535,439
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – commercial and farmland | Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,116	869
Real estate – commercial and farmland | Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	466	787
Real estate – commercial and farmland | Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,934	1,940
Real estate – commercial and farmland | Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	8,790	4,615
Current Loans	1,390,384	463,631
Total Loans	1,399,174	468,246
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – commercial and farmland | Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	3,953	1,190
Real estate – commercial and farmland | Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	402	701
Real estate – commercial and farmland | Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	4,435	2,724
Real estate – residential | Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	14,128	18,754
Current Loans	1,261,073	990,707
Total Loans	1,275,201	1,009,461
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – residential | Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	4,065	8,772
Real estate – residential | Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,428	2,941
Real estate – residential | Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	7,635	7,041
Real estate – residential | Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	19,854	6,627
Current Loans	629,498	243,912
Total Loans	649,352	250,539
Loans 90 Days or More Past Due and Still Accruing	0	0
Real estate – residential | Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	8,854	2,722
Real estate – residential | Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,932	1,585
Real estate – residential | Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	8,068	2,320
Consumer installment | Loans Excluding Purchased Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	3,420	2,357
Current Loans	396,438	322,154
Total Loans	399,858	324,511
Loans 90 Days or More Past Due and Still Accruing	206	0
Consumer installment | Loans Excluding Purchased Loan | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,029	1,556
Consumer installment | Loans Excluding Purchased Loan | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	823	472
Consumer installment | Loans Excluding Purchased Loan | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	568	329
Consumer installment | Purchased Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,610	104
Current Loans	28,077	2,815
Total Loans	29,687	2,919
Loans 90 Days or More Past Due and Still Accruing	0	0
Consumer installment | Purchased Loans | Loans 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	836	57
Consumer installment | Purchased Loans | Loans 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	543	4
Consumer installment | Purchased Loans | Loans 90 or More Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	$ 231	$ 43