Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Summary of loans
Gross loans	$ 9,773,049	$ 9,693,463
Unearned income	(3,672)	(3,825)
Loans, net of unearned income	9,769,377	9,689,638
Commercial, financial, agricultural
Summary of loans
Gross loans	1,424,576	1,367,972
Loans, net of unearned income		1,367,972
Real estate – construction:
Summary of loans
Gross loans	787,895	826,483
Loans, net of unearned income		826,483
Real estate – construction: | Residential
Summary of loans
Gross loans	289,000	289,050
Real estate – construction: | Commercial
Summary of loans
Gross loans	498,895	537,433
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,846,301	2,866,613
Loans, net of unearned income		2,866,613
Real estate – 1-4 family mortgage | Primary
Summary of loans
Gross loans	1,776,436	1,781,948
Real estate – 1-4 family mortgage | Home equity
Summary of loans
Gross loans	563,726	573,540
Real estate – 1-4 family mortgage | Rental/investment
Summary of loans
Gross loans	329,466	335,100
Real estate – 1-4 family mortgage | Land development
Summary of loans
Gross loans	176,673	176,025
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,308,708	4,244,265
Loans, net of unearned income		4,244,265
Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	160,768	156,089
Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	1,662,998	1,637,281
Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	2,484,942	2,450,895
Installment loans to individuals
Summary of loans
Gross loans	317,218	302,430
Loans, net of unearned income		384,305
Purchased loans
Summary of loans
Loans, net of unearned income	1,966,973	2,101,664
Purchased loans | Commercial, financial, agricultural
Summary of loans
Gross loans	280,572	315,619
Purchased loans | Real estate – construction:
Summary of loans
Gross loans	42,829	51,582
Purchased loans | Real estate – construction: | Residential
Summary of loans
Gross loans	11,449	16,407
Purchased loans | Real estate – construction: | Commercial
Summary of loans
Gross loans	31,380	35,175
Purchased loans | Real estate – 1-4 family mortgage
Summary of loans
Gross loans	489,674	516,487
Purchased loans | Real estate – 1-4 family mortgage | Primary
Summary of loans
Gross loans	309,549	332,729
Purchased loans | Real estate – 1-4 family mortgage | Home equity
Summary of loans
Gross loans	114,463	117,275
Purchased loans | Real estate – 1-4 family mortgage | Rental/investment
Summary of loans
Gross loans	44,222	43,169
Purchased loans | Real estate – 1-4 family mortgage | Land development
Summary of loans
Gross loans	21,440	23,314
Purchased loans | Real estate – commercial mortgage:
Summary of loans
Gross loans	1,066,536	1,115,389
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	38,074
Purchased loans | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	418,079	428,077
Purchased loans | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	610,383	647,308
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	38,074	40,004
Purchased loans | Installment loans to individuals
Summary of loans
Gross loans	$ 87,362	$ 102,587