Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 10,933,647	$ 9,689,638
Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	1,514,107	2,101,664
Commercial, financial, agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,536,984	1,367,972
Commercial, financial, agriculture | Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	176,513	315,619
Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	858,104	826,483
Real estate - construction | Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	30,952	51,582
Real estate - construction | Purchased | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,859	16,407
Real estate - construction | Purchased | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	28,093	35,175
Real estate - 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	2,698,308	2,866,613
Real estate - 1-4 family mortgage | Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	341,744	516,487
Real estate - 1-4 family mortgage | Purchased | Primary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	214,770	332,729
Real estate - 1-4 family mortgage | Purchased | Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	80,392	117,275
Real estate - 1-4 family mortgage | Purchased | Rental / Investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	31,928	43,169
Real estate - 1-4 family mortgage | Purchased | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	14,654	23,314
Real estate - commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	4,554,852	4,244,265
Real estate - commercial mortgage | Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	905,223	1,115,389
Real estate - commercial mortgage | Purchased | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	29,454
Real estate - commercial mortgage | Purchased | Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	323,041	428,077
Real estate - commercial mortgage | Purchased | Non-owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	552,728	647,308
Real estate - commercial mortgage | Purchased | Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	29,454	40,004
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	209,537	384,305
Installment loans to individuals | Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, net of unearned income	$ 59,675	$ 102,587