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Allowance for Probable Loan Losses (Portfolio Credit Quality By Loan Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Loan portfolio by credit quality indicator
Portfolio, total	$ 5,886,662	$ 5,950,914
Pass
Loan portfolio by credit quality indicator
Portfolio, total	5,472,887	5,529,707
Special Review
Loan portfolio by credit quality indicator
Portfolio, total	95,420	45,599
Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	62,446	83,069
Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	208,319	232,091
Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	47,591	60,448
Commercial
Loan portfolio by credit quality indicator
Portfolio, total	913,819	966,852
Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	728,696	771,999
Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	92,938	42,152
Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,523	31,539
Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	68,732	90,215
Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	21,931	30,946
Commercial Real Estate: Other Construction and Land Development
Loan portfolio by credit quality indicator
Portfolio, total	1,611,076	1,649,827
Commercial Real Estate: Other Construction and Land Development | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,545,790	1,582,683
Commercial Real Estate: Other Construction and Land Development | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	250	1,164
Commercial Real Estate: Other Construction and Land Development | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total		13,765
Commercial Real Estate: Other Construction and Land Development | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	60,435	45,994
Commercial Real Estate: Other Construction and Land Development | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	4,601	6,221
Commercial Real Estate: Farmland & Commercial
Loan portfolio by credit quality indicator
Portfolio, total	2,003,863	1,995,448
Commercial Real Estate: Farmland & Commercial | Pass
Loan portfolio by credit quality indicator
Portfolio, total	1,852,147	1,849,587
Commercial Real Estate: Farmland & Commercial | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	1,404	2,283
Commercial Real Estate: Farmland & Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	60,687	37,765
Commercial Real Estate: Farmland & Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	78,879	92,008
Commercial Real Estate: Farmland & Commercial | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	10,746	13,806
Commercial Real Estate: Multifamily
Loan portfolio by credit quality indicator
Portfolio, total	118,279	139,448
Commercial Real Estate: Multifamily | Pass
Loan portfolio by credit quality indicator
Portfolio, total	117,587	138,546
Commercial Real Estate: Multifamily | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	121	125
Commercial Real Estate: Multifamily | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	571	777
Residential First Lien
Loan portfolio by credit quality indicator
Portfolio, total	417,682	410,244
Residential First Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	409,950	401,053
Residential First Lien | Special Review
Loan portfolio by credit quality indicator
Portfolio, total	828
Residential First Lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total	152	3,492
Residential First Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	6,752	5,699
Residential Junior Lien
Loan portfolio by credit quality indicator
Portfolio, total	595,839	552,338
Residential Junior Lien | Pass
Loan portfolio by credit quality indicator
Portfolio, total	594,595	551,138
Residential Junior Lien | Watch List - Pass
Loan portfolio by credit quality indicator
Portfolio, total	236
Residential Junior Lien | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total		250
Residential Junior Lien | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,008	950
Consumer
Loan portfolio by credit quality indicator
Portfolio, total	55,996	57,744
Consumer | Pass
Loan portfolio by credit quality indicator
Portfolio, total	54,766	56,440
Consumer | Watch List - Substandard
Loan portfolio by credit quality indicator
Portfolio, total		7
Consumer | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	1,230	1,297
Foreign
Loan portfolio by credit quality indicator
Portfolio, total	170,108	179,013
Foreign | Pass
Loan portfolio by credit quality indicator
Portfolio, total	169,356	178,261
Foreign | Watch - List Impaired
Loan portfolio by credit quality indicator
Portfolio, total	$ 752	$ 752

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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=65884687&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=66008989&loc=d3e5074-111524

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