Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans, net of unearned income:
Gross loans	$ 10,937,807	$ 9,693,463
Unearned income	(4,160)	(3,825)
Loans, net of unearned income	10,933,647	9,689,638
Commercial, financial, agricultural
Loans, net of unearned income:
Gross loans	2,536,984	1,367,972
Loans, net of unearned income	2,536,984	1,367,972
Lease financing
Loans, net of unearned income:
Gross loans	80,022	85,700
Loans, net of unearned income	75,862
Real estate - construction
Loans, net of unearned income:
Gross loans	858,104	826,483
Loans, net of unearned income	858,104	826,483
Real estate - construction | Residential
Loans, net of unearned income:
Gross loans	246,673	289,050
Real estate - construction | Commercial
Loans, net of unearned income:
Gross loans	611,431	537,433
Real estate – 1-4 family mortgage
Loans, net of unearned income:
Gross loans	2,698,308	2,866,613
Loans, net of unearned income	2,698,308	2,866,613
Real estate – 1-4 family mortgage | Primary
Loans, net of unearned income:
Gross loans	1,750,951	1,781,948
Real estate – 1-4 family mortgage | Home Equity Loan
Loans, net of unearned income:
Gross loans	513,160	573,540
Real estate – 1-4 family mortgage | Rental / Investment
Loans, net of unearned income:
Gross loans	296,364	335,100
Real estate – 1-4 family mortgage | Land Development
Loans, net of unearned income:
Gross loans	137,833	176,025
Real estate – commercial mortgage:
Loans, net of unearned income:
Gross loans	4,554,852	4,244,265
Loans, net of unearned income	4,554,852	4,244,265
Real estate – commercial mortgage: | Land Development
Loans, net of unearned income:
Gross loans	149,579	156,089
Real estate – commercial mortgage: | Owner Occupied
Loans, net of unearned income:
Gross loans	1,657,806	1,637,281
Real estate – commercial mortgage: | Non-owner Occupied
Loans, net of unearned income:
Gross loans	2,747,467	2,450,895
Installment loans to individuals
Loans, net of unearned income:
Gross loans	209,537	302,430
Loans, net of unearned income	209,537	384,305
Non-Purchased
Loans, net of unearned income:
Gross loans	9,423,700	7,591,799
Unearned income	(4,160)	(3,825)
Loans, net of unearned income	9,419,540	7,587,974
Non-Purchased | Commercial, financial, agricultural
Loans, net of unearned income:
Gross loans	2,360,471	1,052,353
Non-Purchased | Lease financing
Loans, net of unearned income:
Gross loans	80,022	85,700
Non-Purchased | Real estate - construction
Loans, net of unearned income:
Gross loans	827,152	774,901
Non-Purchased | Real estate - construction | Residential
Loans, net of unearned income:
Gross loans	243,814	272,643
Non-Purchased | Real estate - construction | Commercial
Loans, net of unearned income:
Gross loans	583,338	502,258
Non-Purchased | Real estate – 1-4 family mortgage
Loans, net of unearned income:
Gross loans	2,356,564	2,350,126
Non-Purchased | Real estate – 1-4 family mortgage | Primary
Loans, net of unearned income:
Gross loans	1,536,181	1,449,219
Non-Purchased | Real estate – 1-4 family mortgage | Home Equity Loan
Loans, net of unearned income:
Gross loans	432,768	456,265
Non-Purchased | Real estate – 1-4 family mortgage | Rental / Investment
Loans, net of unearned income:
Gross loans	264,436	291,931
Non-Purchased | Real estate – 1-4 family mortgage | Land Development
Loans, net of unearned income:
Gross loans	123,179	152,711
Non-Purchased | Real estate – 1-4 family mortgage | Land Development
Loans, net of unearned income:
Gross loans	123,179
Non-Purchased | Real estate – commercial mortgage:
Loans, net of unearned income:
Gross loans	3,649,629	3,128,876
Non-Purchased | Real estate – commercial mortgage: | Owner Occupied
Loans, net of unearned income:
Gross loans	1,334,765	1,209,204
Non-Purchased | Real estate – commercial mortgage: | Non-owner Occupied
Loans, net of unearned income:
Gross loans	2,194,739	1,803,587
Non-Purchased | Real estate – commercial mortgage: | Land Development
Loans, net of unearned income:
Gross loans	120,125	116,085
Non-Purchased | Installment loans to individuals
Loans, net of unearned income:
Gross loans	$ 149,862	$ 199,843