Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Summary of loans
Gross loans	$ 10,149,242	$ 10,933,647	$ 10,997,304
Commercial, financial, agricultural
Summary of loans
Gross loans	1,634,633		2,641,598
Real estate – construction:
Summary of loans
Gross loans	1,051,359		791,108
Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	2,702,091		2,788,513
Real estate – commercial mortgage:
Summary of loans
Gross loans	4,530,169		4,410,753
Installment loans to individuals
Summary of loans
Gross loans	156,987		$ 284,553
Purchased loans
Summary of loans
Gross loans	1,256,698	1,514,107
Purchased loans | Commercial, financial, agricultural
Summary of loans
Gross loans	124,725	176,513
Purchased loans | Real estate – construction:
Summary of loans
Gross loans	12,746	30,952
Purchased loans | Real estate – construction: | Residential
Summary of loans
Gross loans	2,564	2,859
Purchased loans | Real estate – construction: | Commercial
Summary of loans
Gross loans	10,182	28,093
Purchased loans | Real estate – 1-4 family mortgage:
Summary of loans
Gross loans	266,517	341,744
Purchased loans | Real estate – 1-4 family mortgage: | Primary
Summary of loans
Gross loans	166,535	214,770
Purchased loans | Real estate – 1-4 family mortgage: | Home equity
Summary of loans
Gross loans	63,088	80,392
Purchased loans | Real estate – 1-4 family mortgage: | Rental/investment
Summary of loans
Gross loans	25,944	31,928
Purchased loans | Real estate – 1-4 family mortgage: | Land development
Summary of loans
Gross loans	10,950	14,654
Purchased loans | Real estate – commercial mortgage:
Summary of loans
Gross loans	806,860	905,223
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	23,902	29,454
Purchased loans | Real estate – commercial mortgage: | Owner-occupied
Summary of loans
Gross loans	290,041	323,041
Purchased loans | Real estate – commercial mortgage: | Non-owner occupied
Summary of loans
Gross loans	492,917	552,728
Purchased loans | Real estate – commercial mortgage: | Land development
Summary of loans
Gross loans	23,902	29,454
Purchased loans | Installment loans to individuals
Summary of loans
Gross loans	$ 45,850	$ 59,675