Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Summary of loans
Gross loans	$ 11,084,738	$ 9,689,638
Commercial, financial, agricultural
Summary of loans
Gross loans	2,648,062	1,367,972
Real estate – construction:
Summary of loans
Gross loans	773,119	826,483
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,760,394	2,866,613
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,577,009	4,244,265
Installment loans to individuals
Summary of loans
Gross loans	243,226	384,305
Purchased loans
Summary of loans
Gross loans	1,660,514	2,101,664
Purchased loans | Commercial, financial, agricultural
Summary of loans
Gross loans	202,768	315,619
Purchased loans | Real estate – construction:
Summary of loans
Gross loans	34,246	51,582
Purchased loans | Real estate – construction: | Residential
Summary of loans
Gross loans	3,093	16,407
Purchased loans | Real estate – construction: | Commercial
Summary of loans
Gross loans	31,153	35,175
Purchased loans | Real estate – 1-4 family mortgage
Summary of loans
Gross loans	391,102	516,487
Purchased loans | Real estate – 1-4 family mortgage | Primary
Summary of loans
Gross loans	245,369	332,729
Purchased loans | Real estate – 1-4 family mortgage | Home equity
Summary of loans
Gross loans	95,235	117,275
Purchased loans | Real estate – 1-4 family mortgage | Rental/investment
Summary of loans
Gross loans	33,567	43,169
Purchased loans | Real estate – 1-4 family mortgage | Land development
Summary of loans
Gross loans	16,931	23,314
Purchased loans | Real estate – commercial mortgage:
Summary of loans
Gross loans	966,367	1,115,389
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	32,694
Purchased loans | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	355,994	428,077
Purchased loans | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	577,679	647,308
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	32,694	40,004
Purchased loans | Installment loans to individuals
Summary of loans
Gross loans	$ 66,031	$ 102,587