Non Purchased Loans - Loan Portfolio Not Subject to Risk Rating (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loan portfolio not subject to risk rating
Loans, net of unearned income	$ 10,933,647	$ 9,689,638
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Loans, net of unearned income	2,536,984	1,367,972
Lease financing
Loan portfolio not subject to risk rating
Loans, net of unearned income	75,862
Real estate - construction
Loan portfolio not subject to risk rating
Loans, net of unearned income	858,104	826,483
Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income	2,698,308	2,866,613
Real estate - commercial mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income	4,554,852	4,244,265
Installment loans to individuals
Loan portfolio not subject to risk rating
Loans, net of unearned income	209,537	384,305
Non-Purchased
Loan portfolio not subject to risk rating
Loans, net of unearned income	$ 9,419,540	7,587,974
Non-Purchased | Performing and Non-Performing
Loan portfolio not subject to risk rating
Loans, net of unearned income		2,933,132
Non-Purchased | Performing and Non-Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Loans, net of unearned income		248,891
Non-Purchased | Performing and Non-Performing | Lease financing
Loan portfolio not subject to risk rating
Loans, net of unearned income		81,875
Non-Purchased | Performing and Non-Performing | Real estate - construction
Loan portfolio not subject to risk rating
Loans, net of unearned income		66,241
Non-Purchased | Performing and Non-Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		2,003,619
Non-Purchased | Performing and Non-Performing | Real estate - commercial mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		332,669
Non-Purchased | Performing and Non-Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Loans, net of unearned income		199,837
Non-Purchased | Performing
Loan portfolio not subject to risk rating
Loans, net of unearned income		2,918,059
Non-Purchased | Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Loans, net of unearned income		247,575
Non-Purchased | Performing | Lease financing
Loan portfolio not subject to risk rating
Loans, net of unearned income		81,649
Non-Purchased | Performing | Real estate - construction
Loan portfolio not subject to risk rating
Loans, net of unearned income		66,241
Non-Purchased | Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		1,992,331
Non-Purchased | Performing | Real estate - commercial mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		330,714
Non-Purchased | Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Loans, net of unearned income		199,549
Non-Purchased | Non- Performing
Loan portfolio not subject to risk rating
Loans, net of unearned income		15,073
Non-Purchased | Non- Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Loans, net of unearned income		1,316
Non-Purchased | Non- Performing | Lease financing
Loan portfolio not subject to risk rating
Loans, net of unearned income		226
Non-Purchased | Non- Performing | Real estate - construction
Loan portfolio not subject to risk rating
Loans, net of unearned income		0
Non-Purchased | Non- Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		11,288
Non-Purchased | Non- Performing | Real estate - commercial mortgage
Loan portfolio not subject to risk rating
Loans, net of unearned income		1,955
Non-Purchased | Non- Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Loans, net of unearned income		$ 288