XML 45 R35.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Allowance for Credit Losses (Impaired Loans) (Details) | Oct. 31, 2022 USD ($) loan | Sep. 30, 2022 USD ($) | Dec. 31, 2021 USD ($)
--- | --- | --- | ---
Loan loss allowances |  |  |
Total troubled debt restructuring |  | $ 2,811,000 | $ 3,253,000
Amount of loans with some degree of payment deferral | $ 54,405,000 |  |
Period of charge off for past due unsecured commercial loans |  | 90 days |
Paycheck protection program loans (COVID-19 program) |  |  |
Loan loss allowances |  |  |
Number of loans | loan | 223 |  |
Amount of loans outstanding | $ 9,292,000 |  |
Real estate - mortgage | Domestic | Residential: first lien |  |  |
Loan loss allowances |  |  |
Total troubled debt restructuring |  | $ 1,658,000 | 2,254,000
Real estate - mortgage | Domestic | Residential Junior Lien |  |  |
Loan loss allowances |  |  |
Total troubled debt restructuring |  | 323,000 | 105,000
Consumer | Domestic |  |  |
Loan loss allowances |  |  |
Total troubled debt restructuring |  | 773,000 | 878,000
Foreign. | Foreign |  |  |
Loan loss allowances |  |  |
Total troubled debt restructuring |  | $ 57,000 | $ 16,000

X
- Definition The amount of loans approved and closed as part of the lending program. + References No definition available. + Details
Name: | iboc_AmountOfLoansApprovedAndClosed
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable with some degree of payment deferrals. + References No definition available. + Details
Name: | iboc_FinancingReceivableWithPaymentDeferrals
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The number of loans approved and closed as part of the lending program. + References No definition available. + Details
Name: | iboc_NumberOfLoansApprovedAndClosed
Namespace Prefix: | iboc_
Data Type: | xbrli:integerItemType
Balance Type: | na
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 Amount of financing receivable modified as troubled debt restructuring. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI https://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554 + Details
Name: | us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Threshold period for when financing receivable is considered past due to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 14 -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447 + Details
Name: | us-gaap_FinancingReceivableThresholdPeriodPastDueWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=iboc_PaycheckProtectionProgramLoansMember
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_GeographicDistributionAxis=us-gaap_GeographicDistributionDomesticMember
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: |