Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 9,086,256	$ 7,623,663
Unearned income	(3,127)	(3,341)
Loans, net of unearned income	9,083,129	7,620,322
Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,693,417	2,031,766
Unearned income	0	0
Loans, net of unearned income	2,693,417	2,031,766
Commercial, financial, agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,295,912	1,039,393
Loans, net of unearned income	1,295,912	1,039,393
Commercial, financial, agricultural \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	420,263	275,570
Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	64,992	57,354
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	740,668	633,389
Loans, net of unearned income	740,668	633,389
Real estate – construction \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	105,149	85,731
Real estate – 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	2,795,343	2,343,721
Loans, net of unearned income	2,795,343	2,343,721
Real estate – 1-4 family mortgage \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	707,453	614,187
Real estate – commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	4,051,509	3,427,530
Loans, net of unearned income	4,051,509	3,427,530
Real estate – commercial mortgage \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	1,423,144	1,037,454
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	137,832	122,276
Loans, net of unearned income	199,697	176,289
Installment loans to individuals \| Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 37,408	$ 18,824

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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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