Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Summary of loans
Gross loans	$ 10,153,267	$ 10,937,807
Unearned income	(4,025)	(4,160)
Loans, net of unearned income	10,149,242	10,933,647	$ 10,997,304
Commercial, financial, agricultural
Summary of loans
Gross loans	1,634,633	2,536,984
Loans, net of unearned income	1,634,633		2,641,598
Lease financing
Summary of loans
Gross loans	78,028	80,022
Loans, net of unearned income	74,003		80,779
Real estate – construction:
Summary of loans
Gross loans	1,051,359	858,104
Loans, net of unearned income	1,051,359		791,108
Real estate – construction: | Residential
Summary of loans
Gross loans	277,163	246,673
Real estate – construction: | Commercial
Summary of loans
Gross loans	774,196	611,431
Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,702,091	2,698,308
Loans, net of unearned income	2,702,091		2,788,513
Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,790,522	1,750,951
Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	489,933	513,160
Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	297,341	296,364
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,530,169	4,554,852
Loans, net of unearned income	4,530,169		4,410,753
Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,663,191	1,657,806
Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,742,029	2,747,467
Installment loans to individuals
Summary of loans
Gross loans	156,987	209,537
Loans, net of unearned income	156,987		$ 284,553
Non purchased loans and leases
Summary of loans
Gross loans	8,896,569	9,423,700
Unearned income	(4,025)	(4,160)
Loans, net of unearned income	8,892,544	9,419,540
Non purchased loans and leases | Paycheck Protection Program
Summary of loans
Loans, net of unearned income	246,931	1,128,703
Non purchased loans and leases | Commercial, financial, agricultural
Summary of loans
Gross loans	1,509,908	2,360,471
Non purchased loans and leases | Lease financing
Summary of loans
Gross loans	78,028	80,022
Non purchased loans and leases | Real estate – construction:
Summary of loans
Gross loans	1,038,613	827,152
Non purchased loans and leases | Real estate – construction: | Residential
Summary of loans
Gross loans	274,599	243,814
Non purchased loans and leases | Real estate – construction: | Commercial
Summary of loans
Gross loans	764,014	583,338
Non purchased loans and leases | Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,435,574	2,356,564
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	1,623,987	1,536,181
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	426,845	432,768
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	271,397	264,436
Non purchased loans and leases | Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	113,345	123,179
Non purchased loans and leases | Real estate – commercial mortgage:
Summary of loans
Gross loans	3,723,309	3,649,629
Non purchased loans and leases | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	101,047	120,125
Non purchased loans and leases | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,373,150	1,334,765
Non purchased loans and leases | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,249,112	2,194,739
Non purchased loans and leases | Installment loans to individuals
Summary of loans
Gross loans	$ 111,137	$ 149,862