XML 48 R37.htm IDEA: XBRL DOCUMENT
v3.5.0.2

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

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition 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 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=iboc_SpecialPassMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_CommercialLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_CommercialRealEstateOtherConstructionAndLandDevelopmentReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_CommercialRealEstateFarmlandAndCommercialReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_CommercialRealEstateMultifamilyReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_ResidentialFirstMortgageFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_ResidentialSecondMortgageFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_ConsumerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=iboc_ForeignReceivablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |