LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 38,189	$ 28,819	$ 25,791
Provision for credit losses	125,488	19,758	16,667
Loans charged off	(54,464)	(19,861)	(21,131)
Recoveries of loans previously charged off	11,548	9,473	7,492
Balance at end of period	199,422	38,189	28,819
Loans individually evaluated for impairment		7,162	4,964
Loans collectively evaluated for impairment		31,027	23,855
Balance at beginning of period	38,189	28,819	25,791
Individually evaluated for impairment		82,475	53,893
Collectively evaluated for impairment		12,609,278	8,370,430
Acquired with deteriorated credit quality		126,723	87,591
Loans, net of unearned income	14,480,925	12,818,476	8,511,914
Balance at end of period	199,422	38,189	28,819
Nonaccrual loans	76,457	75,124
Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	78,661
Balance at end of period		78,661
Balance at beginning of period	78,661
Balance at end of period		78,661
Commercial, financial and agricultural
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	4,567	2,352	2,693
Provision for credit losses	8,963	3,837	(117)
Loans charged off	(10,647)	(3,460)	(1,908)
Recoveries of loans previously charged off	1,889	1,838	1,684
Balance at end of period	7,359	4,567	2,352
Loans individually evaluated for impairment		1,543	191
Loans collectively evaluated for impairment		3,024	2,161
Balance at beginning of period	4,567	2,352	2,693
Individually evaluated for impairment		8,032	1,608
Collectively evaluated for impairment		789,252	676,923
Acquired with deteriorated credit quality		4,887	2,189
Loans, net of unearned income	1,627,477	802,171	680,720
Balance at end of period	7,359	4,567	2,352
Nonaccrual loans	9,836	9,236
Commercial, financial and agricultural | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,587
Balance at end of period		2,587
Balance at beginning of period	2,587
Balance at end of period		2,587
Consumer installment
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	3,784	3,795	1,926
Provision for credit losses	(3,831)	4,268	5,468
Loans charged off	(5,642)	(5,899)	(4,414)
Recoveries of loans previously charged off	1,753	1,620	815
Balance at end of period	4,076	3,784	3,795
Loans individually evaluated for impairment		0	0
Loans collectively evaluated for impairment		3,784	3,795
Balance at beginning of period	3,784	3,795	1,926
Individually evaluated for impairment		0	0
Collectively evaluated for impairment		498,363	482,390
Acquired with deteriorated credit quality		214	169
Loans, net of unearned income	306,995	498,577	482,559
Balance at end of period	4,076	3,784	3,795
Nonaccrual loans	709	831
Consumer installment | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	8,012
Balance at end of period		8,012
Balance at beginning of period	8,012
Balance at end of period		8,012
Indirect automobile
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	0	0	0
Provision for credit losses	(235)	1,459	0
Loans charged off	(3,602)	(1,904)	0
Recoveries of loans previously charged off	1,657	445	0
Balance at end of period	1,929	0	0
Loans individually evaluated for impairment		0	0
Loans collectively evaluated for impairment		0	0
Balance at beginning of period	0	0	0
Individually evaluated for impairment		0	0
Collectively evaluated for impairment		1,056,811	0
Acquired with deteriorated credit quality		5,013	0
Loans, net of unearned income	580,083	1,061,824	0
Balance at end of period	1,929	0	0
Nonaccrual loans	2,831	1,746
Indirect automobile | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	4,109
Balance at end of period		4,109
Balance at beginning of period	4,109
Balance at end of period		4,109
Mortgage warehouse
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	640	640	640
Provision for credit losses	2,563	0	0
Loans charged off	0	0	0
Recoveries of loans previously charged off	0	0	0
Balance at end of period	3,666	640	640
Loans individually evaluated for impairment		0	0
Loans collectively evaluated for impairment		640	640
Balance at beginning of period	640	640	640
Individually evaluated for impairment		0	0
Collectively evaluated for impairment		526,369	360,922
Acquired with deteriorated credit quality		0	0
Loans, net of unearned income	916,353	526,369	360,922
Balance at end of period	3,666	640	640
Mortgage warehouse | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	463
Balance at end of period		463
Balance at beginning of period	463
Balance at end of period		463
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	484	509	519
Provision for credit losses	399	(25)	(10)
Loans charged off	0	0	0
Recoveries of loans previously charged off	0	0	0
Balance at end of period	791	484	509
Loans individually evaluated for impairment		0	0
Loans collectively evaluated for impairment		484	509
Balance at beginning of period	484	509	519
Individually evaluated for impairment		0	0
Collectively evaluated for impairment		564,304	597,945
Acquired with deteriorated credit quality		0	0
Loans, net of unearned income	659,403	564,304	597,945
Balance at end of period	791	484	509
Municipal | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	(92)
Balance at end of period		(92)
Balance at beginning of period	(92)
Balance at end of period		(92)
Premium finance
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,550	1,426	819
Provision for credit losses	(198)	2,721	10,253
Loans charged off	(6,133)	(4,351)	(12,467)
Recoveries of loans previously charged off	3,189	2,754	2,821
Balance at end of period	3,879	2,550	1,426
Loans individually evaluated for impairment		758	379
Loans collectively evaluated for impairment		1,792	1,047
Balance at beginning of period	2,550	1,426	819
Individually evaluated for impairment		6,768	2,360
Collectively evaluated for impairment		647,901	408,021
Acquired with deteriorated credit quality		0	0
Loans, net of unearned income	687,841	654,669	410,381
Balance at end of period	3,879	2,550	1,426
Nonaccrual loans	0	600
Premium finance | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	4,471
Balance at end of period		4,471
Balance at beginning of period	4,471
Balance at end of period		4,471
Real estate – construction and development
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	5,995	4,210	4,743
Provision for credit losses	26,327	454	(514)
Loans charged off	(83)	(414)	(731)
Recoveries of loans previously charged off	817	1,745	712
Balance at end of period	45,304	5,995	4,210
Loans individually evaluated for impairment		204	479
Loans collectively evaluated for impairment		5,791	3,731
Balance at beginning of period	5,995	4,210	4,743
Individually evaluated for impairment		1,605	6,935
Collectively evaluated for impairment		1,532,786	884,258
Acquired with deteriorated credit quality		14,671	7,904
Loans, net of unearned income	1,606,710	1,549,062	899,097
Balance at end of period	45,304	5,995	4,210
Nonaccrual loans	5,407	1,988
Real estate – construction and development | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	12,248
Balance at end of period		12,248
Balance at beginning of period	12,248
Balance at end of period		12,248
Real estate – commercial and farmland
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	9,666	9,659	8,408
Provision for credit losses	78,210	3,017	855
Loans charged off	(27,504)	(3,342)	(356)
Recoveries of loans previously charged off	1,449	332	752
Balance at end of period	88,894	9,666	9,659
Loans individually evaluated for impairment		953	2,274
Loans collectively evaluated for impairment		8,713	7,385
Balance at beginning of period	9,666	9,659	8,408
Individually evaluated for impairment		19,759	17,231
Collectively evaluated for impairment		4,256,397	3,079,049
Acquired with deteriorated credit quality		76,883	56,108
Loans, net of unearned income	5,300,006	4,353,039	3,152,388
Balance at end of period	88,894	9,666	9,659
Nonaccrual loans	18,517	23,797
Real estate – commercial and farmland | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	27,073
Balance at end of period		27,073
Balance at beginning of period	27,073
Balance at end of period		27,073
Real estate – residential
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	10,503	6,228	6,043
Provision for credit losses	13,290	4,027	732
Loans charged off	(853)	(491)	(1,255)
Recoveries of loans previously charged off	794	739	708
Balance at end of period	43,524	10,503	6,228
Loans individually evaluated for impairment		3,704	1,641
Loans collectively evaluated for impairment		6,799	4,587
Balance at beginning of period	10,503	6,228	6,043
Individually evaluated for impairment		46,311	25,759
Collectively evaluated for impairment		2,737,095	1,880,922
Acquired with deteriorated credit quality		25,055	21,221
Loans, net of unearned income	2,796,057	2,808,461	1,927,902
Balance at end of period	43,524	10,503	6,228
Nonaccrual loans	39,157	36,926
Real estate – residential | Accounting Standards Update 2016-13
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	19,790
Balance at end of period		19,790
Balance at beginning of period	19,790
Balance at end of period		19,790
Substandard | Minimum
Allowance for Loan and Lease Losses [Roll Forward]
Nonaccrual loans	100	100	100
Troubled debt restructuring loans	$ 100	$ 100	$ 100