Non Purchased Loans - Aging of Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Past due and nonaccrual loans
Total loans, gross	$ 9,773,049	$ 9,693,463
Unearned income	(3,672)	(3,825)
Loans, net of unearned income	9,769,377	9,689,638
Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	1,424,576	1,367,972
Loans, net of unearned income		1,367,972
Lease financing
Past due and nonaccrual loans
Total loans, gross	88,351	85,700
Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	787,895	826,483
Loans, net of unearned income		826,483
Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	2,846,301	2,866,613
Loans, net of unearned income		2,866,613
Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	4,308,708	4,244,265
Loans, net of unearned income		4,244,265
Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	317,218	302,430
Loans, net of unearned income		384,305
Residential | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	289,000	289,050
Commercial | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	498,895	537,433
Primary | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	1,776,436	1,781,948
Home equity | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	563,726	573,540
Rental/investment | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	329,466	335,100
Land development | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	176,673	176,025
Land development | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	160,768	156,089
Owner-occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	1,662,998	1,637,281
Non-owner occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	2,484,942	2,450,895
Non purchased loans and leases
Past due and nonaccrual loans
Total loans, gross	7,806,076	7,591,799
Unearned income	(3,672)	(3,825)
Loans, net of unearned income	7,802,404	7,587,974
Non purchased loans and leases | Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	1,144,004	1,052,353
Non purchased loans and leases | Lease financing
Past due and nonaccrual loans
Total loans, gross	88,351	85,700
Non purchased loans and leases | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	745,066	774,901
Non purchased loans and leases | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	2,356,627	2,350,126
Non purchased loans and leases | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	3,242,172	3,128,876
Non purchased loans and leases | Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	229,856	199,843
Non purchased loans and leases | Accruing Loans
Past due and nonaccrual loans
Unearned income	(3,672)	(3,825)
Current Loans	7,745,465	7,540,226
Loans, net of unearned income	7,781,020	7,566,465
Non purchased loans and leases | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current, gross	1,135,968	1,045,802
Total loans, gross	1,139,425	1,046,883
Non purchased loans and leases | Accruing Loans | Lease financing
Past due and nonaccrual loans
Current, gross	88,074	85,474
Total loans, gross	88,125	85,474
Non purchased loans and leases | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	741,787	774,107
Total loans, gross	742,338	774,901
Non purchased loans and leases | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	2,322,009	2,320,328
Total loans, gross	2,347,524	2,340,850
Non purchased loans and leases | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	3,232,579	3,119,785
Total loans, gross	3,237,560	3,122,423
Non purchased loans and leases | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current, gross	228,720	198,555
Total loans, gross	229,720	199,759
Non purchased loans and leases | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	3,809	3,635
Loans, net of unearned income	21,384	21,509
Non purchased loans and leases | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current, gross	51	60
Total loans, gross	4,579	5,470
Non purchased loans and leases | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Current, gross	0	0
Total loans, gross	226	226
Non purchased loans and leases | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0	0
Total loans, gross	2,728	0
Non purchased loans and leases | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	3,032	2,082
Total loans, gross	9,103	9,276
Non purchased loans and leases | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	719	1,426
Total loans, gross	4,612	6,453
Non purchased loans and leases | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current, gross	7	67
Total loans, gross	136	84
Non purchased loans and leases | 30-89 Days Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	31,096	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	3,361	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	267	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	22,873	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	3,694	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	901	1,000
Non purchased loans and leases | 30-89 Days Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	1,917	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	118	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	929	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	870	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	0	0
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due	4,459	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	96	476
Non purchased loans and leases | 90 Days or More Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Past due, gross	51	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	284	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	2,642	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	1,287	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	99	204
Non purchased loans and leases | 90 Days or More Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due	15,658	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	4,410	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	226	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	2,728	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	5,142	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	3,023	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	129	17
Non purchased loans and leases | Residential | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	277,551	272,643
Non purchased loans and leases | Residential | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	274,272
Total loans, gross	274,823
Non purchased loans and leases | Residential | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0
Total loans, gross	2,728
Non purchased loans and leases | Residential | 30-89 Days Past Due | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Past due, gross	267
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	284
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	2,728
Non purchased loans and leases | Commercial | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	467,515	502,258
Non purchased loans and leases | Commercial | Accruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	467,515
Total loans, gross	467,515
Non purchased loans and leases | Commercial | Nonaccruing Loans | Real estate – construction:
Past due and nonaccrual loans
Current, gross	0
Total loans, gross	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, gross	1,466,887	1,449,219
Non purchased loans and leases | Primary | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	1,436,829
Total loans, gross	1,458,901
Non purchased loans and leases | Primary | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	2,809
Total loans, gross	7,986
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	20,213
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	898
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	1,859
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	4,279
Non purchased loans and leases | Home equity | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	449,263	456,265
Non purchased loans and leases | Home equity | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	446,756
Total loans, gross	448,660
Non purchased loans and leases | Home equity | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	178
Total loans, gross	603
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	1,184
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	31
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	720
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	394
Non purchased loans and leases | Rental/investment | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	285,244	291,931
Non purchased loans and leases | Rental/investment | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	283,403
Total loans, gross	284,798
Non purchased loans and leases | Rental/investment | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	8
Total loans, gross	446
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	1,339
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	0
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	56
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	438
Non purchased loans and leases | Land development | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Total loans, gross	155,233	152,711
Non purchased loans and leases | Land development | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	122,694	116,085
Non purchased loans and leases | Land development | Accruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	155,021
Total loans, gross	155,165
Non purchased loans and leases | Land development | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	122,047
Total loans, gross	122,589
Non purchased loans and leases | Land development | Nonaccruing Loans | Real estate – 1-4 family mortgage:
Past due and nonaccrual loans
Current, gross	37
Total loans, gross	68
Non purchased loans and leases | Land development | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	0
Total loans, gross	105
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	137
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	464
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	7
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	78
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	31
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	105
Non purchased loans and leases | Owner-occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	1,244,919	1,209,204
Non purchased loans and leases | Owner-occupied | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	1,237,360
Total loans, gross	1,241,117
Non purchased loans and leases | Owner-occupied | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	394
Total loans, gross	3,802
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	2,868
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	870
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	889
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	2,538
Non purchased loans and leases | Non-owner occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	1,874,559	$ 1,803,587
Non purchased loans and leases | Non-owner occupied | Accruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	1,873,172
Total loans, gross	1,873,854
Non purchased loans and leases | Non-owner occupied | Nonaccruing Loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Current, gross	325
Total loans, gross	705
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	362
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	0
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	320
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	$ 380