Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Summary of loans
Gross loans	$ 11,000,796	$ 9,693,463
Commercial, financial, agricultural
Summary of loans
Gross loans	2,641,598	1,367,972
Real estate – construction:
Summary of loans
Gross loans	791,108	826,483
Real estate – construction: | Residential
Summary of loans
Gross loans	295,931	289,050
Real estate – construction: | Commercial
Summary of loans
Gross loans	495,177	537,433
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,788,513	2,866,613
Real estate – 1-4 family mortgage | Primary
Summary of loans
Gross loans	1,756,253	1,781,948
Real estate – 1-4 family mortgage | Home equity
Summary of loans
Gross loans	543,468	573,540
Real estate – 1-4 family mortgage | Rental/investment
Summary of loans
Gross loans	318,803	335,100
Real estate – 1-4 family mortgage | Land development
Summary of loans
Gross loans	169,989	176,025
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,410,753	4,244,265
Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	155,766	156,089
Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,660,674	1,637,281
Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,594,313	2,450,895
Installment loans to individuals
Summary of loans
Gross loans	284,553	302,430
Purchased loans
Summary of loans
Gross loans	1,791,203	2,101,664
Purchased loans | Commercial, financial, agricultural
Summary of loans
Gross loans	225,355	315,619
Purchased loans | Real estate – construction:
Summary of loans
Gross loans	34,236	51,582
Purchased loans | Real estate – construction: | Residential
Summary of loans
Gross loans	3,948	16,407
Purchased loans | Real estate – construction: | Commercial
Summary of loans
Gross loans	30,288	35,175
Purchased loans | Real estate – 1-4 family mortgage
Summary of loans
Gross loans	445,526	516,487
Purchased loans | Real estate – 1-4 family mortgage | Primary
Summary of loans
Gross loans	280,057	332,729
Purchased loans | Real estate – 1-4 family mortgage | Home equity
Summary of loans
Gross loans	102,694	117,275
Purchased loans | Real estate – 1-4 family mortgage | Rental/investment
Summary of loans
Gross loans	41,156	43,169
Purchased loans | Real estate – 1-4 family mortgage | Land development
Summary of loans
Gross loans	21,619	23,314
Purchased loans | Real estate – commercial mortgage:
Summary of loans
Gross loans	1,010,035	1,115,389
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	36,989
Purchased loans | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	390,477	428,077
Purchased loans | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	582,569	647,308
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	36,989	40,004
Purchased loans | Installment loans to individuals
Summary of loans
Gross loans	$ 76,051	$ 102,587