Non Purchased Loans - Aging of Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Past due and nonaccrual loans
Total loans, before unearned income	$ 11,089,067	$ 9,693,463
Unearned income	(4,329)	(3,825)
Loans, net of unearned income	11,084,738	9,689,638
Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, before unearned income	2,648,062	1,367,972
Loans, net of unearned income	2,648,062	1,367,972
Lease financing
Past due and nonaccrual loans
Total loans, before unearned income	87,257	85,700
Loans, net of unearned income	82,928
Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	773,119	826,483
Loans, net of unearned income	773,119	826,483
Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	2,760,394	2,866,613
Loans, net of unearned income	2,760,394	2,866,613
Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	4,577,009	4,244,265
Loans, net of unearned income	4,577,009	4,244,265
Installment loans to individuals
Past due and nonaccrual loans
Total loans, before unearned income	243,226	302,430
Loans, net of unearned income	243,226	384,305
Residential | Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	264,525	289,050
Commercial | Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	508,594	537,433
Primary | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	1,762,897	1,781,948
Home equity | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	537,615	573,540
Rental/investment | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	306,378	335,100
Land development | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	153,504	176,025
Land development | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	150,366	156,089
Owner-occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	1,672,402	1,637,281
Non-owner occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	2,754,241	2,450,895
Non purchased loans and leases
Past due and nonaccrual loans
Total loans, before unearned income	9,428,553	7,591,799
Unearned income	(4,329)	(3,825)
Loans, net of unearned income	9,424,224	7,587,974
Non purchased loans and leases | Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, before unearned income	2,445,294	1,052,353
Non purchased loans and leases | Lease financing
Past due and nonaccrual loans
Total loans, before unearned income	87,257	85,700
Non purchased loans and leases | Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	738,873	774,901
Non purchased loans and leases | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	2,369,292	2,350,126
Non purchased loans and leases | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	3,610,642	3,128,876
Non purchased loans and leases | Installment loans to individuals
Past due and nonaccrual loans
Total loans, before unearned income	177,195	199,843
Non purchased loans and leases | Accruing Loans
Past due and nonaccrual loans
Unearned income	(4,329)	(3,825)
Current Loans	9,393,313	7,540,226
Loans, net of unearned income	9,405,393	7,566,465
Non purchased loans and leases | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current, gross	2,439,040	1,045,802
Total loans, before unearned income	2,440,204	1,046,883
Non purchased loans and leases | Accruing Loans | Lease financing
Past due and nonaccrual loans
Current, gross	87,257	85,474
Total loans, before unearned income	87,257	85,474
Non purchased loans and leases | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	737,885	774,107
Total loans, before unearned income	738,873	774,901
Non purchased loans and leases | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	2,354,020	2,320,328
Total loans, before unearned income	2,359,531	2,340,850
Non purchased loans and leases | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	3,603,465	3,119,785
Total loans, before unearned income	3,606,786	3,122,423
Non purchased loans and leases | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current, gross	175,975	198,555
Total loans, before unearned income	177,071	199,759
Non purchased loans and leases | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	8,279	3,635
Loans, net of unearned income	18,831	21,509
Non purchased loans and leases | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current, gross	1,774	60
Total loans, before unearned income	5,090	5,470
Non purchased loans and leases | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Current, gross	0	0
Total loans, before unearned income	0	226
Non purchased loans and leases | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0	0
Total loans, before unearned income	0	0
Non purchased loans and leases | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	6,094	2,082
Total loans, before unearned income	9,761	9,276
Non purchased loans and leases | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	377	1,426
Total loans, before unearned income	3,856	6,453
Non purchased loans and leases | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current, gross	34	67
Total loans, before unearned income	124	84
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	10,254	22,781
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	876	605
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	988	794
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	4,190	18,020
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	3,277	2,362
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	923	1,000
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	1,246	1,382
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	650	387
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	354	623
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	236	372
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	6	0
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	1,826	3,458
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	288	476
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	1,321	2,502
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	44	276
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	173	204
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	9,306	16,492
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Past due, gross	2,666	5,023
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	0	226
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0	0
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	3,313	6,571
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	3,243	4,655
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Past due, gross	84	17
Non purchased loans and leases | Residential | Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	261,432	272,643
Non purchased loans and leases | Residential | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	260,444
Total loans, before unearned income	261,432
Non purchased loans and leases | Residential | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0
Total loans, before unearned income	0
Non purchased loans and leases | Residential | 30-89 Days Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	988
Non purchased loans and leases | Residential | 30-89 Days Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Residential | 90 Days or More Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Residential | 90 Days or More Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Commercial | Real estate – construction:
Past due and nonaccrual loans
Total loans, before unearned income	477,441	502,258
Non purchased loans and leases | Commercial | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	477,441
Total loans, before unearned income	477,441
Non purchased loans and leases | Commercial | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0
Total loans, before unearned income	0
Non purchased loans and leases | Commercial | 30-89 Days Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Commercial | 30-89 Days Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Commercial | 90 Days or More Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Commercial | 90 Days or More Past Due | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Primary | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	1,517,528	1,449,219
Non purchased loans and leases | Primary | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	1,505,737
Total loans, before unearned income	1,508,630
Non purchased loans and leases | Primary | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	5,520
Total loans, before unearned income	8,898
Non purchased loans and leases | Primary | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	1,795
Non purchased loans and leases | Primary | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	347
Non purchased loans and leases | Primary | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	1,098
Non purchased loans and leases | Primary | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	3,031
Non purchased loans and leases | Home equity | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	442,380	456,265
Non purchased loans and leases | Home equity | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	440,820
Total loans, before unearned income	441,837
Non purchased loans and leases | Home equity | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	451
Total loans, before unearned income	543
Non purchased loans and leases | Home equity | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	1,001
Non purchased loans and leases | Home equity | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Home equity | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	16
Non purchased loans and leases | Home equity | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	92
Non purchased loans and leases | Rental/investment | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	272,811	291,931
Non purchased loans and leases | Rental/investment | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	270,995
Total loans, before unearned income	272,536
Non purchased loans and leases | Rental/investment | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	90
Total loans, before unearned income	275
Non purchased loans and leases | Rental/investment | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	1,334
Non purchased loans and leases | Rental/investment | 30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	7
Non purchased loans and leases | Rental/investment | 90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	207
Non purchased loans and leases | Rental/investment | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	178
Non purchased loans and leases | Land development | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	136,573	152,711
Non purchased loans and leases | Land development | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	117,672	116,085
Non purchased loans and leases | Land development | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	136,468
Total loans, before unearned income	136,528
Non purchased loans and leases | Land development | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	117,287
Total loans, before unearned income	117,587
Non purchased loans and leases | Land development | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	33
Total loans, before unearned income	45
Non purchased loans and leases | Land development | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	46
Total loans, before unearned income	85
Non purchased loans and leases | Land development | 30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	60
Non purchased loans and leases | Land development | 30-89 Days Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	257
Non purchased loans and leases | 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 loans and leases | Land development | 30-89 Days Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | 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 loans and leases | Land development | 90 Days or More Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	43
Non purchased loans and leases | Land development | 90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Past due, gross	12
Non purchased loans and leases | Land development | 90 Days or More Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	39
Non purchased loans and leases | Owner-occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	1,316,408	1,209,204
Non purchased loans and leases | Owner-occupied | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	1,312,024
Total loans, before unearned income	1,313,059
Non purchased loans and leases | Owner-occupied | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	276
Total loans, before unearned income	3,349
Non purchased loans and leases | Owner-occupied | 30-89 Days Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	1,034
Non purchased loans and leases | Owner-occupied | 30-89 Days Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	178
Non purchased loans and leases | Owner-occupied | 90 Days or More Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	1
Non purchased loans and leases | Owner-occupied | 90 Days or More Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	2,895
Non purchased loans and leases | Non-owner occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, before unearned income	2,176,562	$ 1,803,587
Non purchased loans and leases | Non-owner occupied | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	2,174,154
Total loans, before unearned income	2,176,140
Non purchased loans and leases | Non-owner occupied | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	55
Total loans, before unearned income	422
Non purchased loans and leases | Non-owner occupied | 30-89 Days Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	1,986
Non purchased loans and leases | Non-owner occupied | 30-89 Days Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	58
Non purchased loans and leases | Non-owner occupied | 90 Days or More Past Due | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	0
Non purchased loans and leases | Non-owner occupied | 90 Days or More Past Due | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Past due, gross	$ 309