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
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
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
Purchased loans
Past due and nonaccrual loans
Loans, net of unearned income	1,966,973	2,101,664
Purchased loans | Accruing loans
Past due and nonaccrual loans
Current Loans	1,928,351	2,075,422
Loans, net of unearned income	1,947,883	2,094,626
Purchased loans | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	14,428	14,887
Purchased loans | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	5,104	4,317
Purchased loans | Nonaccruing loans
Past due and nonaccrual loans
Current Loans	8,911	2,250
Loans, net of unearned income	19,090	7,038
Purchased loans | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	2,595	606
Purchased loans | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	7,584	4,182
Purchased loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	280,572	315,619
Purchased loans | Commercial, financial, agricultural | Accruing loans
Past due and nonaccrual loans
Current, gross	269,348	311,218
Total loans, gross	274,616	314,105
Purchased loans | Commercial, financial, agricultural | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	2,284	1,889
Purchased loans | Commercial, financial, agricultural | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	2,984	998
Purchased loans | Commercial, financial, agricultural | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	3,585	268
Total loans, gross	5,956	1,514
Purchased loans | Commercial, financial, agricultural | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	820	0
Purchased loans | Commercial, financial, agricultural | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	1,551	1,246
Purchased loans | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	42,829	51,582
Purchased loans | Real estate – construction: | Accruing loans
Past due and nonaccrual loans
Current, gross	42,182	51,263
Total loans, gross	42,829	51,582
Purchased loans | Real estate – construction: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	647	319
Purchased loans | Real estate – construction: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0	0
Purchased loans | Real estate – construction: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	0	0
Total loans, gross	0	0
Purchased loans | Real estate – construction: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	0	0
Purchased loans | Real estate – construction: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0	0
Purchased loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	489,674	516,487
Purchased loans | Real estate – 1-4 family mortgage | Accruing loans
Past due and nonaccrual loans
Current, gross	474,980	503,826
Total loans, gross	481,118	511,586
Purchased loans | Real estate – 1-4 family mortgage | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	5,727	5,516
Purchased loans | Real estate – 1-4 family mortgage | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	411	2,244
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	2,090	1,534
Total loans, gross	8,556	4,901
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	1,492	605
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	4,974	2,762
Purchased loans | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	1,066,536	1,115,389
Purchased loans | Real estate – commercial mortgage: | Accruing loans
Past due and nonaccrual loans
Current, gross	1,058,128	1,110,570
Total loans, gross	1,062,226	1,114,946
Purchased loans | Real estate – commercial mortgage: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	2,479	3,454
Purchased loans | Real estate – commercial mortgage: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	1,619	922
Purchased loans | Real estate – commercial mortgage: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	3,052	320
Total loans, gross	4,310	443
Purchased loans | Real estate – commercial mortgage: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	272	0
Purchased loans | Real estate – commercial mortgage: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	986	123
Purchased loans | Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	87,362	102,587
Purchased loans | Installment loans to individuals | Accruing loans
Past due and nonaccrual loans
Current, gross	83,713	98,545
Total loans, gross	87,094	102,407
Purchased loans | Installment loans to individuals | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	3,291	3,709
Purchased loans | Installment loans to individuals | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	90	153
Purchased loans | Installment loans to individuals | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	184	128
Total loans, gross	268	180
Purchased loans | Installment loans to individuals | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	11	1
Purchased loans | Installment loans to individuals | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	73	51
Purchased loans | Residential | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	11,449	16,407
Purchased loans | Residential | Real estate – construction: | Accruing loans
Past due and nonaccrual loans
Current, gross	10,802
Total loans, gross	11,449
Purchased loans | Residential | Real estate – construction: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	647
Purchased loans | Residential | Real estate – construction: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Residential | Real estate – construction: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	0
Total loans, gross	0
Purchased loans | Residential | Real estate – construction: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Residential | Real estate – construction: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Commercial | Real estate – construction:
Past due and nonaccrual loans
Total loans, gross	31,380	35,175
Purchased loans | Commercial | Real estate – construction: | Accruing loans
Past due and nonaccrual loans
Current, gross	31,380
Total loans, gross	31,380
Purchased loans | Commercial | Real estate – construction: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Commercial | Real estate – construction: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Commercial | Real estate – construction: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	0
Total loans, gross	0
Purchased loans | Commercial | Real estate – construction: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Commercial | Real estate – construction: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Primary | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	309,549	332,729
Purchased loans | Primary | Real estate – 1-4 family mortgage | Accruing loans
Past due and nonaccrual loans
Current, gross	297,809
Total loans, gross	303,628
Purchased loans | Primary | Real estate – 1-4 family mortgage | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	5,507
Purchased loans | Primary | Real estate – 1-4 family mortgage | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	312
Purchased loans | Primary | Real estate – 1-4 family mortgage | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	966
Total loans, gross	5,921
Purchased loans | Primary | Real estate – 1-4 family mortgage | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	1,191
Purchased loans | Primary | Real estate – 1-4 family mortgage | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	3,764
Purchased loans | Home equity | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	114,463	117,275
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Accruing loans
Past due and nonaccrual loans
Current, gross	112,902
Total loans, gross	113,036
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	65
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	69
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	749
Total loans, gross	1,427
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	200
Purchased loans | Home equity | Real estate – 1-4 family mortgage | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	478
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	44,222	43,169
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Accruing loans
Past due and nonaccrual loans
Current, gross	43,214
Total loans, gross	43,346
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	102
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	30
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	90
Total loans, gross	876
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	54
Purchased loans | Rental/investment | Real estate – 1-4 family mortgage | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	732
Purchased loans | Land development | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	21,440	23,314
Purchased loans | Land development | Real estate – 1-4 family mortgage | Accruing loans
Past due and nonaccrual loans
Current, gross	21,055
Total loans, gross	21,108
Purchased loans | Land development | Real estate – 1-4 family mortgage | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	53
Purchased loans | Land development | Real estate – 1-4 family mortgage | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Land development | Real estate – 1-4 family mortgage | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	285
Total loans, gross	332
Purchased loans | Land development | Real estate – 1-4 family mortgage | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	47
Purchased loans | Land development | Real estate – 1-4 family mortgage | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Land development | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	38,074
Purchased loans | Land development | Real estate – commercial mortgage: | Accruing loans
Past due and nonaccrual loans
Current, gross	36,980
Total loans, gross	37,656
Purchased loans | Land development | Real estate – commercial mortgage: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	604
Purchased loans | Land development | Real estate – commercial mortgage: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	72
Purchased loans | Land development | Real estate – commercial mortgage: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	254
Total loans, gross	418
Purchased loans | Land development | Real estate – commercial mortgage: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	0
Purchased loans | Land development | Real estate – commercial mortgage: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	164
Purchased loans | Owner-occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	418,079	428,077
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Accruing loans
Past due and nonaccrual loans
Current, gross	412,188
Total loans, gross	415,041
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	1,356
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	1,497
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	2,652
Total loans, gross	3,038
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	261
Purchased loans | Owner-occupied | Real estate – commercial mortgage: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	125
Purchased loans | Non-owner occupied | Real estate – commercial mortgage:
Past due and nonaccrual loans
Total loans, gross	610,383	$ 647,308
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Accruing loans
Past due and nonaccrual loans
Current, gross	608,960
Total loans, gross	609,529
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Accruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	519
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Accruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	50
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Nonaccruing loans
Past due and nonaccrual loans
Current, gross	146
Total loans, gross	854
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Nonaccruing loans | 30-89 Days Past Due
Past due and nonaccrual loans
Past due, gross	11
Purchased loans | Non-owner occupied | Real estate – commercial mortgage: | Nonaccruing loans | 90 Days or More Past Due
Past due and nonaccrual loans
Past due, gross	$ 697