Non Purchased Loans - Loan Portfolio Not Subject to Risk Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Loan portfolio not subject to risk rating
Loans, net of unearned income	$ 10,149,242	$ 10,933,647	$ 10,997,304
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Loans, net of unearned income	1,634,633		2,641,598
Lease financing
Loan portfolio not subject to risk rating
Loans, net of unearned income	74,003		80,779
Real estate – construction:
Loan portfolio not subject to risk rating
Loans, net of unearned income	1,051,359		791,108
Real estate – 1-4 family mortgage:
Loan portfolio not subject to risk rating
Loans, net of unearned income	2,702,091		2,788,513
Real estate – commercial mortgage:
Loan portfolio not subject to risk rating
Loans, net of unearned income	4,530,169		4,410,753
Installment loans to individuals
Loan portfolio not subject to risk rating
Loans, net of unearned income	156,987		$ 284,553
Non purchased loans and leases
Loan portfolio not subject to risk rating
Loans, net of unearned income	$ 8,892,544	$ 9,419,540