Non Purchased Loans - Summary of Non-purchased Loans and Leases (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
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
Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	85,700	64,992
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 – 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 – 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
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
Non-Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	7,591,799	6,392,839
Unearned income	(3,825)	(3,127)
Loans, net of unearned income	7,587,974	6,389,712
Non-Purchased \| Commercial, financial, agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,052,353	875,649
Non-Purchased \| Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	85,700	64,992
Non-Purchased \| Real estate – construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	774,901	635,519
Non-Purchased \| Real estate – 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,350,126	2,087,890
Non-Purchased \| Real estate – commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	3,128,876	2,628,365
Non-Purchased \| Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 199,843	$ 100,424

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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 of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes 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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