LOANS - Loans by Risk Grade (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 14,599,805,000	$ 14,480,925,000
9
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total		0
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	406,640,000	1,034,506,000
Year two	634,188,000	138,136,000
Year three	124,380,000	100,900,000
Year four	101,325,000	68,339,000
Year five	59,715,000	28,655,000
Prior	65,422,000	45,190,000
Revolving Loans Amortized Cost Basis	219,359,000	211,751,000
Total	1,611,029,000	1,627,477,000
Commercial, financial and agricultural | 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	329,750,000	829,710,000
Year two	483,062,000	2,912,000
Year three	2,631,000	1,055,000
Year four	983,000	387,000
Year five	295,000	490,000
Prior	5,290,000	4,961,000
Revolving Loans Amortized Cost Basis	63,365,000	36,373,000
Total	885,376,000	875,888,000
Commercial, financial and agricultural | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	7,799,000	1,213,000
Year two	449,000	1,512,000
Year three	8,991,000	668,000
Year four	638,000	996,000
Year five	810,000	172,000
Prior	976,000	967,000
Revolving Loans Amortized Cost Basis	10,771,000	14,317,000
Total	30,434,000	19,845,000
Commercial, financial and agricultural | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	30,638,000	109,352,000
Year two	69,131,000	54,266,000
Year three	43,563,000	16,932,000
Year four	14,490,000	17,968,000
Year five	17,168,000	7,027,000
Prior	9,080,000	3,905,000
Revolving Loans Amortized Cost Basis	61,094,000	68,806,000
Total	245,164,000	278,256,000
Commercial, financial and agricultural | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	38,031,000	86,837,000
Year two	74,263,000	71,645,000
Year three	59,189,000	74,388,000
Year four	77,684,000	37,779,000
Year five	30,449,000	15,359,000
Prior	35,375,000	23,069,000
Revolving Loans Amortized Cost Basis	75,733,000	85,366,000
Total	390,724,000	394,443,000
Commercial, financial and agricultural | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	76,000	4,061,000
Year two	4,191,000	4,269,000
Year three	4,543,000	4,772,000
Year four	4,374,000	7,443,000
Year five	6,345,000	804,000
Prior	4,493,000	5,842,000
Revolving Loans Amortized Cost Basis	6,431,000	4,352,000
Total	30,453,000	31,543,000
Commercial, financial and agricultural | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	3,000	21,000
Year two	12,000	72,000
Year three	1,673,000	506,000
Year four	470,000	193,000
Year five	576,000	3,509,000
Prior	3,847,000	1,232,000
Revolving Loans Amortized Cost Basis	397,000	632,000
Total	6,978,000	6,165,000
Commercial, financial and agricultural | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	343,000	3,312,000
Year two	3,080,000	3,460,000
Year three	3,790,000	2,579,000
Year four	2,686,000	3,573,000
Year five	4,072,000	1,294,000
Prior	6,361,000	5,214,000
Revolving Loans Amortized Cost Basis	1,568,000	1,886,000
Total	21,900,000	21,318,000
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		19,000
Total		19,000
Consumer installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	18,855,000	142,833,000
Year two	104,935,000	63,892,000
Year three	55,120,000	57,725,000
Year four	39,591,000	17,936,000
Year five	15,393,000	4,808,000
Prior	14,614,000	11,042,000
Revolving Loans Amortized Cost Basis	8,589,000	8,759,000
Total	257,097,000	306,995,000
Consumer installment | 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	1,597,000	6,782,000
Year two	5,577,000	3,001,000
Year three	2,625,000	1,550,000
Year four	1,308,000	583,000
Year five	510,000	95,000
Prior	33,000	1,000
Revolving Loans Amortized Cost Basis	155,000	667,000
Total	11,805,000	12,679,000
Consumer installment | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	46,000
Year four	33,000	2,000
Year five	1,000	0
Prior	58,000	63,000
Revolving Loans Amortized Cost Basis	41,000	42,000
Total	133,000	153,000
Consumer installment | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	5,983,000	15,172,000
Year two	11,263,000	6,960,000
Year three	5,382,000	2,838,000
Year four	2,045,000	887,000
Year five	647,000	1,455,000
Prior	1,921,000	601,000
Revolving Loans Amortized Cost Basis	4,991,000	4,389,000
Total	32,232,000	32,302,000
Consumer installment | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	11,275,000	120,800,000
Year two	87,762,000	53,593,000
Year three	46,500,000	53,182,000
Year four	35,996,000	16,329,000
Year five	14,116,000	3,121,000
Prior	11,715,000	9,437,000
Revolving Loans Amortized Cost Basis	3,308,000	3,556,000
Total	210,672,000	260,018,000
Consumer installment | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	49,000
Year two	46,000	127,000
Year three	86,000	28,000
Year four	12,000	30,000
Year five	25,000	3,000
Prior	163,000	242,000
Revolving Loans Amortized Cost Basis	0	8,000
Total	332,000	487,000
Consumer installment | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	2,000
Year three	0	9,000
Year four	9,000	0
Year five	0	0
Prior	143,000	145,000
Revolving Loans Amortized Cost Basis	6,000	0
Total	158,000	156,000
Consumer installment | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	30,000
Year two	287,000	209,000
Year three	525,000	72,000
Year four	188,000	105,000
Year five	94,000	134,000
Prior	581,000	553,000
Revolving Loans Amortized Cost Basis	86,000	97,000
Total	1,761,000	1,200,000
Indirect automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	35,595,000
Year three	31,611,000	188,313,000
Year four	162,987,000	188,964,000
Year five	159,987,000	110,066,000
Prior	128,052,000	57,145,000
Revolving Loans Amortized Cost Basis	0	0
Total	482,637,000	580,083,000
Indirect automobile | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	81,000
Year four	75,000	31,000
Year five	29,000	5,356,000
Prior	6,512,000	3,054,000
Revolving Loans Amortized Cost Basis	0	0
Total	6,616,000	8,522,000
Indirect automobile | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	35,432,000
Year three	31,573,000	187,656,000
Year four	162,594,000	188,302,000
Year five	159,571,000	103,570,000
Prior	119,905,000	52,781,000
Revolving Loans Amortized Cost Basis	0	0
Total	473,643,000	567,741,000
Indirect automobile | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	57,000
Year four	30,000	70,000
Year five	33,000	62,000
Prior	101,000	85,000
Revolving Loans Amortized Cost Basis	0	0
Total	164,000	274,000
Indirect automobile | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	163,000
Year three	38,000	519,000
Year four	288,000	561,000
Year five	354,000	1,078,000
Prior	1,534,000	1,225,000
Revolving Loans Amortized Cost Basis	0	0
Total	2,214,000	3,546,000
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	880,216,000	916,353,000
Total	880,216,000	916,353,000
Mortgage warehouse | 3
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	880,216,000	916,353,000
Total	880,216,000	916,353,000
Municipal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	25,045,000	236,076,000
Year two	232,551,000	13,398,000
Year three	12,247,000	8,944,000
Year four	8,540,000	149,194,000
Year five	146,668,000	141,543,000
Prior	234,177,000	110,248,000
Revolving Loans Amortized Cost Basis	0	0
Total	659,228,000	659,403,000
Municipal | 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	25,045,000	91,692,000
Year two	91,812,000	12,685,000
Year three	11,565,000	8,944,000
Year four	8,540,000	143,741,000
Year five	141,216,000	124,929,000
Prior	205,673,000	97,923,000
Revolving Loans Amortized Cost Basis	0	0
Total	483,851,000	479,914,000
Municipal | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	73,000,000
Year two	72,903,000	0
Year three	0	0
Year four	0	0
Year five	0	9,410,000
Prior	13,012,000	0
Revolving Loans Amortized Cost Basis	0	0
Total	85,915,000	82,410,000
Municipal | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	39,990,000
Year two	61,551,000	713,000
Year three	682,000	0
Year four	0	5,453,000
Year five	5,452,000	7,204,000
Prior	12,648,000	5,489,000
Revolving Loans Amortized Cost Basis	0	0
Total	80,333,000	58,849,000
Municipal | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	31,394,000
Year two	6,285,000	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	2,844,000	6,836,000
Revolving Loans Amortized Cost Basis	0	0
Total	9,129,000	38,230,000
Premium finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	351,490,000	667,425,000
Year two	344,077,000	18,996,000
Year three	9,817,000	515,000
Year four	257,000	746,000
Year five	638,000	121,000
Prior	100,000	38,000
Revolving Loans Amortized Cost Basis	0	0
Total	706,379,000	687,841,000
Premium finance | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	351,490,000	661,614,000
Year two	340,097,000	18,236,000
Year three	9,738,000	515,000
Year four	257,000	746,000
Year five	638,000	121,000
Prior	100,000	38,000
Revolving Loans Amortized Cost Basis	0	0
Total	702,320,000	681,270,000
Premium finance | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	5,811,000
Year two	3,980,000	760,000
Year three	79,000	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	4,059,000	6,571,000
Real estate – construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	183,254,000	666,893,000
Year two	590,210,000	483,145,000
Year three	391,084,000	226,138,000
Year four	181,490,000	73,061,000
Year five	67,908,000	35,841,000
Prior	80,319,000	51,658,000
Revolving Loans Amortized Cost Basis	38,969,000	69,974,000
Total	1,533,234,000	1,606,710,000
Real estate – construction and development | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0
Year two	62,000
Year three	0
Year four	0
Year five	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	62,000
Real estate – construction and development | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	14,018,000	59,325,000
Year two	42,007,000	7,035,000
Year three	6,565,000	6,870,000
Year four	4,269,000	8,046,000
Year five	3,444,000	3,415,000
Prior	11,263,000	6,916,000
Revolving Loans Amortized Cost Basis	873,000	1,293,000
Total	82,439,000	92,900,000
Real estate – construction and development | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	168,849,000	605,254,000
Year two	545,742,000	445,496,000
Year three	362,783,000	205,444,000
Year four	132,341,000	50,181,000
Year five	49,482,000	14,672,000
Prior	35,491,000	26,915,000
Revolving Loans Amortized Cost Basis	37,990,000	68,574,000
Total	1,332,678,000	1,416,536,000
Real estate – construction and development | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	387,000	1,614,000
Year two	2,136,000	26,720,000
Year three	17,825,000	9,612,000
Year four	38,407,000	13,261,000
Year five	13,755,000	17,712,000
Prior	29,389,000	10,127,000
Revolving Loans Amortized Cost Basis	106,000	107,000
Total	102,005,000	79,153,000
Real estate – construction and development | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	685,000
Year two	120,000	1,036,000
Year three	892,000	3,646,000
Year four	5,991,000	1,302,000
Year five	598,000	0
Prior	1,194,000	4,564,000
Revolving Loans Amortized Cost Basis	0	0
Total	8,795,000	11,233,000
Real estate – construction and development | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	15,000
Year two	143,000	2,858,000
Year three	3,019,000	566,000
Year four	482,000	271,000
Year five	629,000	42,000
Prior	2,982,000	3,136,000
Revolving Loans Amortized Cost Basis	0	0
Total	7,255,000	6,888,000
Real estate – construction and development | 9
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0
Year two	0
Year three	2,000
Year four	0
Year five	0
Prior	0
Revolving Loans Amortized Cost Basis	2,000
Total	4,000
Real estate – commercial and farmland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	275,760,000	1,275,475,000
Year two	1,327,200,000	1,060,392,000
Year three	1,139,526,000	660,156,000
Year four	685,396,000	655,451,000
Year five	629,847,000	531,935,000
Prior	1,458,087,000	1,012,521,000
Revolving Loans Amortized Cost Basis	101,010,000	104,076,000
Total	5,616,826,000	5,300,006,000
Real estate – commercial and farmland | 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	0
Year three	0	161,000
Year four	156,000	0
Year five	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	156,000	161,000
Real estate – commercial and farmland | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	7,482,000
Year two	7,352,000	540,000
Year three	380,000	521,000
Year four	448,000	2,131,000
Year five	2,094,000	4,375,000
Prior	13,262,000	10,663,000
Revolving Loans Amortized Cost Basis	17,000	1,138,000
Total	23,553,000	26,850,000
Real estate – commercial and farmland | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	186,578,000	918,939,000
Year two	928,268,000	370,703,000
Year three	414,458,000	143,591,000
Year four	181,807,000	197,942,000
Year five	248,378,000	224,712,000
Prior	515,131,000	274,665,000
Revolving Loans Amortized Cost Basis	52,651,000	67,067,000
Total	2,527,271,000	2,197,619,000
Real estate – commercial and farmland | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	87,859,000	344,777,000
Year two	366,846,000	584,814,000
Year three	563,285,000	423,241,000
Year four	396,659,000	331,024,000
Year five	255,335,000	242,573,000
Prior	671,363,000	545,745,000
Revolving Loans Amortized Cost Basis	43,474,000	34,326,000
Total	2,384,821,000	2,506,500,000
Real estate – commercial and farmland | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	1,323,000	4,027,000
Year two	17,020,000	39,216,000
Year three	96,085,000	69,173,000
Year four	71,810,000	80,726,000
Year five	63,286,000	25,561,000
Prior	142,589,000	94,461,000
Revolving Loans Amortized Cost Basis	4,223,000	1,274,000
Total	396,336,000	314,438,000
Real estate – commercial and farmland | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	0
Year two	0	10,680,000
Year three	10,313,000	4,895,000
Year four	15,984,000	28,139,000
Year five	47,716,000	7,670,000
Prior	38,807,000	31,224,000
Revolving Loans Amortized Cost Basis	3,000	0
Total	112,823,000	82,608,000
Real estate – commercial and farmland | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	250,000
Year two	7,714,000	54,439,000
Year three	55,005,000	18,574,000
Year four	18,532,000	15,489,000
Year five	13,038,000	27,044,000
Prior	76,935,000	55,763,000
Revolving Loans Amortized Cost Basis	642,000	271,000
Total	171,866,000	171,830,000
Real estate – residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	303,348,000	786,803,000
Year two	773,309,000	562,538,000
Year three	492,413,000	287,286,000
Year four	240,415,000	206,739,000
Year five	178,277,000	173,832,000
Prior	619,739,000	522,873,000
Revolving Loans Amortized Cost Basis	245,658,000	255,986,000
Total	2,853,159,000	2,796,057,000
Real estate – residential | 1
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	17,000	19,000
Revolving Loans Amortized Cost Basis	0	0
Total	17,000	19,000
Real estate – residential | 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	0	37,000
Year two	36,000	398,000
Year three	388,000	12,000
Year four	11,000	121,000
Year five	99,000	1,275,000
Prior	42,503,000	47,286,000
Revolving Loans Amortized Cost Basis	1,313,000	1,402,000
Total	44,350,000	50,531,000
Real estate – residential | 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	296,261,000	763,101,000
Year two	731,149,000	529,268,000
Year three	434,948,000	254,632,000
Year four	202,552,000	186,531,000
Year five	154,099,000	154,285,000
Prior	467,379,000	388,825,000
Revolving Loans Amortized Cost Basis	197,899,000	203,491,000
Total	2,484,287,000	2,480,133,000
Real estate – residential | 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	5,768,000	19,296,000
Year two	29,740,000	19,874,000
Year three	17,636,000	15,784,000
Year four	14,464,000	11,607,000
Year five	10,104,000	14,240,000
Prior	61,238,000	53,869,000
Revolving Loans Amortized Cost Basis	40,174,000	44,276,000
Total	179,124,000	178,946,000
Real estate – residential | 5
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	481,000	400,000
Year two	8,581,000	1,768,000
Year three	28,055,000	3,489,000
Year four	9,476,000	3,479,000
Year five	9,202,000	1,151,000
Prior	28,452,000	12,824,000
Revolving Loans Amortized Cost Basis	3,523,000	3,618,000
Total	87,770,000	26,729,000
Real estate – residential | 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	49,000	527,000
Year two	418,000	1,843,000
Year three	951,000	1,030,000
Year four	881,000	334,000
Year five	367,000	724,000
Prior	3,520,000	3,391,000
Revolving Loans Amortized Cost Basis	107,000	255,000
Total	6,293,000	8,104,000
Real estate – residential | 7
Accounts, Notes, Loans and Financing Receivable [Line Items]
Year one	789,000	3,442,000
Year two	3,385,000	9,387,000
Year three	10,435,000	12,339,000
Year four	13,031,000	4,667,000
Year five	4,406,000	2,157,000
Prior	16,630,000	16,659,000
Revolving Loans Amortized Cost Basis	2,642,000	2,944,000
Total	$ 51,318,000	$ 51,595,000