XML 44 R33.htm IDEA: XBRL DOCUMENT
v3.21.1

Allowance for Credit Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | $ 2,681 | $ 19,447
Loans Individually Evaluated for Impairment, Allowance | 279 | 279
Loans Collectively Evaluated for Impairment, Recorded Investment | 7,459,677 | 7,522,307
Loans Collectively Evaluated for Impairment, Allowance | 108,129 | 108,780
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 1,055 | 1,189
Loans Individually Evaluated for Impairment, Allowance | 209 | 209
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,739,552 | 1,784,747
Loans Collectively Evaluated for Impairment, Allowance | 21,954 | 21,699
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 422 | 439
Loans Collectively Evaluated for Impairment, Recorded Investment | 2,420,870 | 2,288,869
Loans Collectively Evaluated for Impairment, Allowance | 32,203 | 30,000
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member] |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 127 | 134
Loans Collectively Evaluated for Impairment, Recorded Investment | 518,857 | 440,910
Loans Collectively Evaluated for Impairment, Allowance | 5,935 | 5,051
Real estate - construction | Domestic | 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 | 892 | 17,496
Loans Individually Evaluated for Impairment, Allowance | 70 | 70
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,652,526 | 1,829,261
Loans Collectively Evaluated for Impairment, Allowance | 34,336 | 37,542
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 147 | 151
Loans Collectively Evaluated for Impairment, Recorded Investment | 401,549 | 404,968
Loans Collectively Evaluated for Impairment, Allowance | 3,917 | 3,874
Real estate - mortgage | Domestic | Residential Junior Lien |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 38 | 38
Loans Collectively Evaluated for Impairment, Recorded Investment | 549,048 | 593,987
Loans Collectively Evaluated for Impairment, Allowance | 8,736 | 9,570
Consumer | Domestic |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Collectively Evaluated for Impairment, Recorded Investment | 39,743 | 40,595
Loans Collectively Evaluated for Impairment, Allowance | 279 | 291
Foreign | Foreign |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Collectively Evaluated for Impairment, Recorded Investment | 137,532 | 138,970
Loans Collectively Evaluated for Impairment, Allowance | $ 769 | $ 753

X
- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&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_FinancingReceivablePortfolioSegmentAxis=iboc_CommercialFinancialAndAgriculturalRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GeographicDistributionAxis=us-gaap_GeographicDistributionDomesticMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LienCategoryAxis=us-gaap_SeniorLienMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LienCategoryAxis=us-gaap_JuniorLienMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=iboc_ForeignPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GeographicDistributionAxis=us-gaap_GeographicDistributionForeignMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |