Purchased Loans - Summary of Purchased Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Summary of loans
Gross loans	$ 7,701,432	$ 7,623,663
Unearned income	(3,362)	(3,341)
Loans, net of unearned income	7,698,070	7,620,322
Purchased loans
Summary of loans
Gross loans	1,867,948	2,031,766
Unearned income	0	0
Loans, net of unearned income	1,867,948	2,031,766
Commercial, financial, agricultural
Summary of loans
Gross loans	1,046,818	1,039,393
Loans, net of unearned income	1,046,818	1,039,393
Commercial, financial, agricultural \| Purchased loans
Summary of loans
Gross loans	243,672	275,570
Loans, net of unearned income	243,672	275,570
Real estate – construction
Summary of loans
Gross loans	657,491	633,389
Loans, net of unearned income	657,491	633,389
Real estate – construction \| Purchased loans
Summary of loans
Gross loans	75,061	85,731
Loans, net of unearned income	75,061	85,731
Real estate – 1-4 family mortgage
Summary of loans
Gross loans	2,358,101	2,343,721
Loans, net of unearned income	2,358,101	2,343,721
Real estate – 1-4 family mortgage \| Purchased loans
Summary of loans
Gross loans	572,830	614,187
Loans, net of unearned income	572,830	614,187
Real estate – commercial mortgage
Summary of loans
Gross loans	3,463,953	3,427,530
Loans, net of unearned income	3,463,953	3,427,530
Real estate – commercial mortgage \| Purchased loans
Summary of loans
Gross loans	960,273	1,037,454
Loans, net of unearned income	960,273	1,037,454
Installment loans to individuals
Summary of loans
Gross loans	119,171	122,276
Loans, net of unearned income	171,707	176,289
Installment loans to individuals \| Purchased loans
Summary of loans
Gross loans	16,112	18,824
Loans, net of unearned income	$ 16,112	$ 18,824

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159169&loc=d3e10152-111534

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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