Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Summary of loans
Gross loans	$ 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
Summary of loans
Gross loans	2,648,062	1,367,972
Loans, net of unearned income	2,648,062	1,367,972
Lease financing
Summary of loans
Gross loans	87,257	85,700
Loans, net of unearned income	82,928
Real estate – construction:
Summary of loans
Gross loans	773,119	826,483
Loans, net of unearned income	773,119	826,483
Real estate – construction: | Residential
Summary of loans
Gross loans	264,525	289,050
Real estate – construction: | Commercial
Summary of loans
Gross loans	508,594	537,433
Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,760,394	2,866,613
Loans, net of unearned income	2,760,394	2,866,613
Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,762,897	1,781,948
Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	537,615	573,540
Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	306,378	335,100
Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	153,504	176,025
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,577,009	4,244,265
Loans, net of unearned income	4,577,009	4,244,265
Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	150,366	156,089
Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,672,402	1,637,281
Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,754,241	2,450,895
Installment loans to individuals
Summary of loans
Gross loans	243,226	302,430
Loans, net of unearned income	243,226	384,305
Non purchased loans and leases
Summary of loans
Gross loans	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
Summary of loans
Gross loans	2,445,294	1,052,353
Non purchased loans and leases | Lease financing
Summary of loans
Gross loans	87,257	85,700
Non purchased loans and leases | Real estate – construction:
Summary of loans
Gross loans	738,873	774,901
Non purchased loans and leases | Real estate – construction: | Residential
Summary of loans
Gross loans	261,432	272,643
Non purchased loans and leases | Real estate – construction: | Commercial
Summary of loans
Gross loans	477,441	502,258
Non purchased loans and leases | Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,369,292	2,350,126
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,517,528	1,449,219
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	442,380	456,265
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	272,811	291,931
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	136,573	152,711
Non purchased loans and leases | Real estate – commercial mortgage:
Summary of loans
Gross loans	3,610,642	3,128,876
Non purchased loans and leases | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	117,672	116,085
Non purchased loans and leases | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,316,408	1,209,204
Non purchased loans and leases | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,176,562	1,803,587
Non purchased loans and leases | Installment loans to individuals
Summary of loans
Gross loans	$ 177,195	$ 199,843