Non Purchased Loans - Aging of Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Past due and nonaccrual loans
Gross loans	$ 10,937,807	$ 9,693,463
Unearned income	(4,160)	(3,825)
Loans, net of unearned income	10,933,647	9,689,638
Commercial, financial, agricultural
Past due and nonaccrual loans
Gross loans	2,536,984	1,367,972
Loans, net of unearned income	2,536,984	1,367,972
Lease financing
Past due and nonaccrual loans
Gross loans	80,022	85,700
Loans, net of unearned income	75,862
Real estate - construction
Past due and nonaccrual loans
Gross loans	858,104	826,483
Loans, net of unearned income	858,104	826,483
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	2,698,308	2,866,613
Loans, net of unearned income	2,698,308	2,866,613
Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	4,554,852	4,244,265
Loans, net of unearned income	4,554,852	4,244,265
Installment loans to individuals
Past due and nonaccrual loans
Gross loans	209,537	302,430
Loans, net of unearned income	209,537	384,305
Primary | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	1,750,951	1,781,948
Home Equity Loan | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	513,160	573,540
Rental/investment | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	296,364	335,100
Owner-occupied | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	1,657,806	1,637,281
Non-owner Occupied | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	2,747,467	2,450,895
Residential | Real estate - construction
Past due and nonaccrual loans
Gross loans	246,673	289,050
Commercial | Real estate - construction
Past due and nonaccrual loans
Gross loans	611,431	537,433
Non-Purchased
Past due and nonaccrual loans
Gross loans	9,423,700	7,591,799
Unearned income	(4,160)	(3,825)
Loans, net of unearned income	9,419,540	7,587,974
Non-Purchased | Commercial, financial, agricultural
Past due and nonaccrual loans
Gross loans	2,360,471	1,052,353
Non-Purchased | Lease financing
Past due and nonaccrual loans
Gross loans	80,022	85,700
Non-Purchased | Real estate - construction
Past due and nonaccrual loans
Gross loans	827,152	774,901
Non-Purchased | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	2,356,564	2,350,126
Non-Purchased | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	3,649,629	3,128,876
Non-Purchased | Installment loans to individuals
Past due and nonaccrual loans
Gross loans	149,862	199,843
Non-Purchased | Accruing Loans
Past due and nonaccrual loans
Unearned income	(4,160)	(3,825)
Current Loans	9,377,753	7,540,226
Loans, net of unearned income	9,399,171	7,566,465
Non-Purchased | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current loans	2,354,716	1,045,802
Gross loans	2,356,071	1,046,883
Non-Purchased | Accruing Loans | Lease financing
Past due and nonaccrual loans
Current loans	79,974	85,474
Gross loans	79,974	85,474
Non-Purchased | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	826,655	774,107
Gross loans	826,655	774,901
Non-Purchased | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	2,330,533	2,320,328
Gross loans	2,346,658	2,340,850
Non-Purchased | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	3,641,415	3,119,785
Gross loans	3,644,266	3,122,423
Non-Purchased | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current loans	148,620	198,555
Gross loans	149,707	199,759
Non-Purchased | Nonaccruing Loans
Past due and nonaccrual loans
Unearned income	0
Current Loans	7,826	3,635
Loans, net of unearned income	20,369	21,509
Non-Purchased | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current loans	2,432	60
Gross loans	4,400	5,470
Non-Purchased | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Current loans	0	0
Gross loans	48	226
Non-Purchased | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	0	0
Gross loans	497	0
Non-Purchased | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	4,865	2,082
Gross loans	9,906	9,276
Non-Purchased | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	495	1,426
Gross loans	5,363	6,453
Non-Purchased | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current loans	34	67
Gross loans	155	84
Non-Purchased | 30-89 Days Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	17,635	22,781
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	1,124	605
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0	794
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	13,801	18,020
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	1,814	2,362
Non-Purchased | 30-89 Days Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	896	1,000
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	2,204	1,382
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	164	387
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0	0
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	1,992	623
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	44	372
Non-Purchased | 30-89 Days Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	4	0
Non-Purchased | 90 Days or More Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	3,783	3,458
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	231	476
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0	0
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	2,324	2,502
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	1,037	276
Non-Purchased | 90 Days or More Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	191	204
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	10,339	16,492
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	1,804	5,023
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	48	226
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	497	0
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	3,049	6,571
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	4,824	4,655
Non-Purchased | 90 Days or More Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	117	17
Non-Purchased | Primary | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	1,536,181	1,449,219
Non-Purchased | Primary | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	1,513,716
Gross loans	1,527,359
Non-Purchased | Primary | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	4,213
Gross loans	8,822
Non-Purchased | Primary | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	11,889
Non-Purchased | Primary | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	1,865
Non-Purchased | Primary | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	1,754
Non-Purchased | Primary | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	2,744
Non-Purchased | Home Equity Loan | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	432,768	456,265
Non-Purchased | Home Equity Loan | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	430,702
Gross loans	432,214
Non-Purchased | Home Equity Loan | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	377
Gross loans	554
Non-Purchased | Home Equity Loan | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	1,152
Non-Purchased | Home Equity Loan | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	66
Non-Purchased | Home Equity Loan | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	360
Non-Purchased | Home Equity Loan | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	111
Non-Purchased | Rental/investment | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	264,436	291,931
Non-Purchased | Rental/investment | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	263,064
Gross loans	263,937
Non-Purchased | Rental/investment | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	244
Gross loans	499
Non-Purchased | Rental/investment | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	663
Non-Purchased | Rental/investment | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	61
Non-Purchased | Rental/investment | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	210
Non-Purchased | Rental/investment | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	194
Non-Purchased | Land Development | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Gross loans	123,179
Non-Purchased | Land Development | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	120,125	116,085
Non-Purchased | Land Development | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	123,051
Gross loans	123,148
Non-Purchased | Land Development | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	119,820
Gross loans	120,048
Non-Purchased | Land Development | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current loans	31
Gross loans	31
Non-Purchased | Land Development | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	4
Gross loans	77
Non-Purchased | Land Development | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	97
Non-Purchased | Land Development | 30-89 Days Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	113
Non-Purchased | Land Development | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Land Development | 30-89 Days Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	44
Non-Purchased | Land Development | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Land Development | 90 Days or More Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	115
Non-Purchased | Land Development | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Land Development | 90 Days or More Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	29
Non-Purchased | Owner-occupied | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	1,334,765	1,209,204
Non-Purchased | Owner-occupied | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	1,330,155
Gross loans	1,331,729
Non-Purchased | Owner-occupied | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	438
Gross loans	3,036
Non-Purchased | Owner-occupied | 30-89 Days Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	779
Non-Purchased | Owner-occupied | 30-89 Days Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Owner-occupied | 90 Days or More Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	795
Non-Purchased | Owner-occupied | 90 Days or More Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	2,598
Non-Purchased | Non-owner Occupied | Real estate - commercial mortgage
Past due and nonaccrual loans
Gross loans	2,194,739	1,803,587
Non-Purchased | Non-owner Occupied | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	2,191,440
Gross loans	2,192,489
Non-Purchased | Non-owner Occupied | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Current loans	53
Gross loans	2,250
Non-Purchased | Non-owner Occupied | 30-89 Days Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	922
Non-Purchased | Non-owner Occupied | 30-89 Days Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Non-owner Occupied | 90 Days or More Past Due | Accruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	127
Non-Purchased | Non-owner Occupied | 90 Days or More Past Due | Nonaccruing Loans | Real estate - commercial mortgage
Past due and nonaccrual loans
Past due, gross	2,197
Non-Purchased | Residential | Real estate - construction
Past due and nonaccrual loans
Gross loans	243,814	272,643
Non-Purchased | Residential | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	243,317
Gross loans	243,317
Non-Purchased | Residential | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	0
Gross loans	497
Non-Purchased | Residential | 30-89 Days Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Residential | 30-89 Days Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Residential | 90 Days or More Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Residential | 90 Days or More Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	497
Non-Purchased | Commercial | Real estate - construction
Past due and nonaccrual loans
Gross loans	583,338	$ 502,258
Non-Purchased | Commercial | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	583,338
Gross loans	583,338
Non-Purchased | Commercial | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Current loans	0
Gross loans	0
Non-Purchased | Commercial | 30-89 Days Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Commercial | 30-89 Days Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Commercial | 90 Days or More Past Due | Accruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	0
Non-Purchased | Commercial | 90 Days or More Past Due | Nonaccruing Loans | Real estate - construction
Past due and nonaccrual loans
Past due, gross	$ 0