Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 9,693,463	$ 9,086,256
Unearned income	(3,825)	(3,127)
Loans, net of unearned income	9,689,638	9,083,129
Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,101,664	2,693,417
Unearned income	0	0
Loans, net of unearned income	2,101,664	2,693,417
Commercial, financial, agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,367,972	1,295,912
Loans, net of unearned income	1,367,972	1,295,912
Commercial, financial, agricultural \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	315,619	420,263
Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	85,700	64,992
Lease financing \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	0	0
Real estate – construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	826,483	740,668
Loans, net of unearned income	826,483	740,668
Real estate – construction \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	51,582	105,149
Real estate – 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,866,613	2,795,343
Loans, net of unearned income	2,866,613	2,795,343
Real estate – 1-4 family mortgage \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	516,487	707,453
Real estate – commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	4,244,265	4,051,509
Loans, net of unearned income	4,244,265	4,051,509
Real estate – commercial mortgage \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,115,389	1,423,144
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	302,430	137,832
Loans, net of unearned income	384,305	199,697
Installment loans to individuals \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 102,587	$ 37,408

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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