Non Purchased Loans - Loan Portfolio Not Subject to Risk Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Loan portfolio not subject to risk rating
Total loans, net of unearned income	$ 10,688,408	$ 10,933,647	$ 9,769,377
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total loans, net of unearned income	2,249,287		1,424,576
Lease financing
Loan portfolio not subject to risk rating
Total loans, net of unearned income	75,256		84,679
Real estate – construction:
Loan portfolio not subject to risk rating
Total loans, net of unearned income	955,918		787,895
Real estate – 1-4 family mortgage:
Loan portfolio not subject to risk rating
Total loans, net of unearned income	2,686,061		2,846,301
Real estate – commercial mortgage:
Loan portfolio not subject to risk rating
Total loans, net of unearned income	4,549,027		4,308,708
Installment loans to individuals
Loan portfolio not subject to risk rating
Total loans, net of unearned income	172,859		$ 317,218
Non purchased loans and leases
Loan portfolio not subject to risk rating
Total loans, net of unearned income	$ 9,292,502	$ 9,419,540