Non Purchased Loans - Summary of Non-Purchased Loans and Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Summary of loans
Gross loans	$ 9,317,448	$ 9,086,256
Unearned income	(3,664)	(3,127)
Loans, net of unearned income	9,313,784	9,083,129
Commercial, financial, agricultural
Summary of loans
Gross loans	1,328,560	1,295,912
Loans, net of unearned income	1,328,560	1,295,912
Lease financing
Summary of loans
Gross loans	73,617	64,992
Real estate – construction
Summary of loans
Gross loans	816,695	740,668
Loans, net of unearned income	816,695	740,668
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,797,633	2,795,343
Loans, net of unearned income	2,797,633	2,795,343
Real estate – commercial mortgage
Summary of loans
Gross loans	4,022,375	4,051,509
Loans, net of unearned income	4,022,375	4,051,509
Installment loans to individuals
Summary of loans
Gross loans	278,568	137,832
Loans, net of unearned income	348,521	199,697
Non purchased loans and leases
Summary of loans
Gross loans	7,035,482	6,392,839
Unearned income	(3,664)	(3,127)
Loans, net of unearned income	7,031,818	6,389,712
Non purchased loans and leases \| Commercial, financial, agricultural
Summary of loans
Gross loans	988,867	875,649
Non purchased loans and leases \| Lease financing
Summary of loans
Gross loans	73,617	64,992
Non purchased loans and leases \| Real estate – construction
Summary of loans
Gross loans	764,589	635,519
Non purchased loans and leases \| Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,235,908	2,087,890
Non purchased loans and leases \| Real estate – commercial mortgage
Summary of loans
Gross loans	2,809,470	2,628,365
Non purchased loans and leases \| Installment loans to individuals
Summary of loans
Gross loans	$ 163,031	$ 100,424

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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