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Allowance for Probable Loan Losses (Details 6) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) item	Dec. 31, 2014 USD ($)
Loan portfolio by credit quality indicator
Portfolio, total	$ 5,922,972	$ 5,679,245
Pass
Loan portfolio by credit quality indicator
Portfolio, total	5,544,825	5,328,410
Special Review
Loan portfolio by credit quality indicator
Portfolio, total	5,724	54,561
Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	72,364	37,674
Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	243,677	182,429
Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	56,382	76,171
Commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,012,391	1,089,486
Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	867,908	961,490
Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total		38,382
Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	22,793	3,793
Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	90,425	45,646
Commercial | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	31,265	40,175
Commercial Real Estate: Other Construction and Land Development
Loan portfolio by credit quality indicator
Portfolio, total	1,655,249	1,414,977
Commercial Real Estate: Other Construction and Land Development | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,586,892	1,353,971
Commercial Real Estate: Other Construction and Land Development | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	327	1,005
Commercial Real Estate: Other Construction and Land Development | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	12,278	10,428
Commercial Real Estate: Other Construction and Land Development | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	49,403	38,697
Commercial Real Estate: Other Construction and Land Development | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	6,349	10,876
Commercial real estate: farmland and commercial
Loan portfolio by credit quality indicator
Portfolio, total	1,952,708	1,901,399
Commercial real estate: farmland and commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,800,442	1,754,741
Commercial real estate: farmland and commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	5,397	11,674
Commercial real estate: farmland and commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	37,293	23,453
Commercial real estate: farmland and commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	99,934	97,365
Commercial real estate: farmland and commercial | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	9,642	14,166
Commercial real estate: multifamily
Loan portfolio by credit quality indicator
Portfolio, total	108,282	116,699
Commercial real estate: multifamily | Pass
Loan portfolio by credit quality indicator
Portfolio, total	107,335	115,729
Commercial real estate: multifamily | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	135	135
Commercial real estate: multifamily | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	812	835
Residential: first lien
Loan portfolio by credit quality indicator
Portfolio, total	409,276	422,026
Residential: first lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	400,468	412,668
Residential: first lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total		3,500
Residential: first lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	3,514	18
Residential: first lien | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	5,294	5,840
Residential: junior lien
Loan portfolio by credit quality indicator
Portfolio, total	539,424	488,300
Residential: junior lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	538,140	484,968
Residential: junior lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	256	437
Residential: junior lien | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,028	2,895
Consumer
Loan portfolio by credit quality indicator
Portfolio, total	58,286	61,137
Consumer | Pass
Loan portfolio by credit quality indicator
Portfolio, total	57,033	59,622
Consumer | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	10	131
Consumer | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,243	1,384
Foreign
Loan portfolio by credit quality indicator
Portfolio, total	187,356	185,221
Foreign | Pass
Loan portfolio by credit quality indicator
Portfolio, total	186,607	$ 185,221
Foreign | Watch List - Impaired
Loan portfolio by credit quality indicator
Portfolio, total	$ 749
Commercial real estate | Watch List - Impaired
Loan portfolio by credit quality indicator
Number of loan foreclosures | item	2

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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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 310



-SubTopic 10



-Section 45



-Paragraph 2



-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522



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=35738203&loc=d3e5074-111524

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