Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Summary of loans
Gross loans	$ 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
Summary of loans
Gross loans	1,424,576	1,367,972
Loans, net of unearned income		1,367,972
Lease financing
Summary of loans
Gross loans	88,351	85,700
Real estate – construction:
Summary of loans
Gross loans	787,895	826,483
Loans, net of unearned income		826,483
Real estate – construction: | Residential
Summary of loans
Gross loans	289,000	289,050
Real estate – construction: | Commercial
Summary of loans
Gross loans	498,895	537,433
Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,846,301	2,866,613
Loans, net of unearned income		2,866,613
Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,776,436	1,781,948
Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	563,726	573,540
Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	329,466	335,100
Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	176,673	176,025
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,308,708	4,244,265
Loans, net of unearned income		4,244,265
Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	160,768	156,089
Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,662,998	1,637,281
Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,484,942	2,450,895
Installment loans to individuals
Summary of loans
Gross loans	317,218	302,430
Loans, net of unearned income		384,305
Non purchased loans and leases
Summary of loans
Gross loans	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
Summary of loans
Gross loans	1,144,004	1,052,353
Non purchased loans and leases | Lease financing
Summary of loans
Gross loans	88,351	85,700
Non purchased loans and leases | Real estate – construction:
Summary of loans
Gross loans	745,066	774,901
Non purchased loans and leases | Real estate – construction: | Residential
Summary of loans
Gross loans	277,551	272,643
Non purchased loans and leases | Real estate – construction: | Commercial
Summary of loans
Gross loans	467,515	502,258
Non purchased loans and leases | Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,356,627	2,350,126
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,466,887	1,449,219
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	449,263	456,265
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	285,244	291,931
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	155,233	152,711
Non purchased loans and leases | Real estate – commercial mortgage:
Summary of loans
Gross loans	3,242,172	3,128,876
Non purchased loans and leases | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	122,694	116,085
Non purchased loans and leases | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,244,919	1,209,204
Non purchased loans and leases | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	1,874,559	1,803,587
Non purchased loans and leases | Installment loans to individuals
Summary of loans
Gross loans	$ 229,856	$ 199,843