XML 78 R63.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | $ 63,204 | $ 48,405
Loans Individually Evaluated for Impairment, Allowance | 434 | 961
Loans Collectively Evaluated for Impairment, Recorded Investment | 6,284,968 | 5,916,283
Loans Collectively Evaluated for Impairment, Allowance | 67,253 | 63,700
Commercial |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 17,947 | 22,412
Loans Individually Evaluated for Impairment, Allowance | 300 |
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,068,520 | 887,255
Loans Collectively Evaluated for Impairment, Allowance | 27,605 | 25,649
Commercial Real Estate: Other Construction and Land Development |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 2,455 | 4,776
Loans Individually Evaluated for Impairment, Allowance | 116 | 371
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,681,095 | 1,712,099
Loans Collectively Evaluated for Impairment, Allowance | 11,559 | 13,518
Commercial Real Estate: Farmland & Commercial |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 33,123 | 10,810
Loans Individually Evaluated for Impairment, Allowance | 18 | 546
Loans Collectively Evaluated for Impairment, Recorded Investment | 2,010,162 | 1,932,260
Loans Collectively Evaluated for Impairment, Allowance | 16,645 | 16,185
Commercial Real Estate: Multifamily |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 476 | 552
Loans Collectively Evaluated for Impairment, Recorded Investment | 192,440 | 139,914
Loans Collectively Evaluated for Impairment, Allowance | 1,109 | 806
Residential First Lien |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 6,852 | 6,836
Loans Individually Evaluated for Impairment, Allowance |  | 44
Loans Collectively Evaluated for Impairment, Recorded Investment | 425,925 | 415,068
Loans Collectively Evaluated for Impairment, Allowance | 2,950 | 2,411
Residential Junior Lien |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 723 | 978
Loans Collectively Evaluated for Impairment, Recorded Investment | 700,025 | 609,340
Loans Collectively Evaluated for Impairment, Allowance | 6,103 | 3,716
Consumer |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 1,281 | 1,295
Loans Collectively Evaluated for Impairment, Recorded Investment | 48,262 | 53,873
Loans Collectively Evaluated for Impairment, Allowance | 440 | 531
Foreign |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 347 | 746
Loans Collectively Evaluated for Impairment, Recorded Investment | 158,539 | 166,474
Loans Collectively Evaluated for Impairment, Allowance | $ 842 | $ 884

X
- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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: |