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Allowance for Probable Loan Losses (Credit Quality Indicator) (Details) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Loan portfolio by credit quality indicator |  |
Portfolio, total | $ 5,950,914 | $ 5,679,245
Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 5,529,707 | 5,328,410
Special Review |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 45,599 | 54,561
Watch List - Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 83,069 | 37,674
Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 232,091 | 182,429
Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 60,448 | 76,171
Commercial |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 966,852 | 1,089,486
Commercial | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 771,999 | 961,490
Commercial | Special Review |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 42,152 | 38,382
Commercial | Watch List - Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 31,539 | 3,793
Commercial | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 90,215 | 45,646
Commercial | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 30,946 | 40,175
Commercial Real Estate: Other Construction and Land Development |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,649,827 | 1,414,977
Commercial Real Estate: Other Construction and Land Development | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,582,683 | 1,353,971
Commercial Real Estate: Other Construction and Land Development | Special Review |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,164 | 1,005
Commercial Real Estate: Other Construction and Land Development | Watch List - Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 13,765 | 10,428
Commercial Real Estate: Other Construction and Land Development | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 45,994 | 38,697
Commercial Real Estate: Other Construction and Land Development | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 6,221 | 10,876
Commercial real estate: farmland and commercial |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,995,448 | 1,901,399
Commercial real estate: farmland and commercial | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,849,587 | 1,754,741
Commercial real estate: farmland and commercial | Special Review |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 2,283 | 11,674
Commercial real estate: farmland and commercial | Watch List - Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 37,765 | 23,453
Commercial real estate: farmland and commercial | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 92,008 | 97,365
Commercial real estate: farmland and commercial | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 13,806 | 14,166
Commercial real estate: multifamily |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 139,448 | 116,699
Commercial real estate: multifamily | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 138,546 | 115,729
Commercial real estate: multifamily | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 125 | 135
Commercial real estate: multifamily | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 777 | 835
Residential: first lien |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 410,244 | 422,026
Residential: first lien | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 401,053 | 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 | 3,492 | 18
Residential: first lien | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 5,699 | 5,840
Residential: junior lien |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 552,338 | 488,300
Residential: junior lien | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 551,138 | 484,968
Residential: junior lien | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 250 | 437
Residential: junior lien | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 950 | 2,895
Consumer |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 57,744 | 61,137
Consumer | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 56,440 | 59,622
Consumer | Watch List - Substandard |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 7 | 131
Consumer | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 1,297 | 1,384
Foreign |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 179,013 | 185,221
Foreign | Pass |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | 178,261 | $ 185,221
Foreign | Watch List - Impaired |  |
Loan portfolio by credit quality indicator |  |
Portfolio, total | $ 752 |

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