Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Summary of loans
Gross loans	$ 9,126,211	$ 7,623,663
Unearned income	(3,304)	(3,341)
Loans, net of unearned income	9,122,907	7,620,322
Commercial, financial, agricultural
Summary of loans
Gross loans	1,313,344	1,039,393
Loans, net of unearned income	1,313,344	1,039,393
Lease financing
Summary of loans
Gross loans	57,576	57,354
Real estate – construction
Summary of loans
Gross loans	736,985	633,389
Loans, net of unearned income	736,985	633,389
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,762,683	2,343,721
Loans, net of unearned income	2,762,683	2,343,721
Real estate – commercial mortgage
Summary of loans
Gross loans	4,112,585	3,427,530
Loans, net of unearned income	4,112,585	3,427,530
Installment loans to individuals
Summary of loans
Gross loans	143,038	122,276
Loans, net of unearned income	197,310	176,289
Non purchased loans and leases
Summary of loans
Gross loans	6,213,542	5,591,897
Unearned income	(3,304)	(3,341)
Loans, net of unearned income	6,210,238	5,588,556
Non purchased loans and leases \| Commercial, financial, agricultural
Summary of loans
Gross loans	817,799	763,823
Non purchased loans and leases \| Lease financing
Summary of loans
Gross loans	57,576	57,354
Non purchased loans and leases \| Real estate – construction
Summary of loans
Gross loans	624,892	547,658
Non purchased loans and leases \| Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,000,770	1,729,534
Non purchased loans and leases \| Real estate – commercial mortgage
Summary of loans
Gross loans	2,609,510	2,390,076
Non purchased loans and leases \| Installment loans to individuals
Summary of loans
Gross loans	$ 102,995	$ 103,452

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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