XML 46 R35.htm IDEA: XBRL DOCUMENT
v3.25.2

Allowance for Credit Losses - By Loan Class (Details) - USD ($) $ in Thousands | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Mar. 31, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Dec. 31, 2024
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | $ 158,707 | $ 142,798 | $ 156,537 | $ 157,069 | $ 157,069
Losses charged to allowance |  | (9,978) | (4,260) | (11,977) | (32,084) |
Recoveries credited to allowance |  | 1,856 | 1,300 | 2,696 | 1,875 |
Net (losses) recoveries charged to allowance |  | (8,122) | (2,960) | (9,281) | (30,209) |
Credit loss expense |  | 4,398 | 8,771 | 7,727 | 21,749 |
Balance at the end of the period | $ 142,798 | 154,983 | 148,609 | 154,983 | 148,609 | 156,537
Commercial, financial and agricultural | Commercial |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Charge-down due to customer filing bankruptcy | 25,600 |  |  |  |  |
Commercial, financial and agricultural | Domestic | Commercial |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 28,946 | 26,676 | 29,853 | 35,550 | 35,550
Losses charged to allowance |  | (1,749) | (1,979) | (3,537) | (29,720) | (34,149)
Recoveries credited to allowance |  | 1,626 | 1,234 | 2,447 | 1,789 |
Net (losses) recoveries charged to allowance |  | (123) | (745) | (1,090) | (27,931) |
Credit loss expense |  | (409) | 1,324 | (349) | 19,636 |
Balance at the end of the period | 26,676 | 28,414 | 27,255 | 28,414 | 27,255 | 29,853
Commercial, financial and agricultural | Domestic | Commercial real estate: farmland & commercial |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 45,667 | 39,402 | 43,990 | 42,703 | 42,703
Recoveries credited to allowance |  | 106 | 6 | 112 | 10 |
Net (losses) recoveries charged to allowance |  | 106 | 6 | 112 | 10 |
Credit loss expense |  | 887 | 5,480 | 2,558 | 2,175 |
Balance at the end of the period | 39,402 | 46,660 | 44,888 | 46,660 | 44,888 | 43,990
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member] |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 4,857 | 3,768 | 4,869 | 5,088 | 5,088
Credit loss expense |  | 3,143 | (240) | 3,131 | (1,560) |
Balance at the end of the period | 3,768 | 8,000 | 3,528 | 8,000 | 3,528 | 4,869
Commercial real estate | Domestic | Commercial real estate construction development |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 61,865 | 55,097 | 60,639 | 55,291 | 55,291
Losses charged to allowance |  | (8,121) | (2,228) | (8,121) | (2,228) | (2,228)
Net (losses) recoveries charged to allowance |  | (8,121) | (2,228) | (8,121) | (2,228) |
Credit loss expense |  | 321 | 1,971 | 1,547 | 1,777 |
Balance at the end of the period | 55,097 | 54,065 | 54,840 | 54,065 | 54,840 | 60,639
Real estate - mortgage | Domestic | Residential First Lien |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 5,669 | 5,757 | 5,528 | 5,812 | 5,812
Losses charged to allowance |  | (3) | (1) | (49) | (46) | (46)
Recoveries credited to allowance |  | 13 | 34 | 15 | 36 |
Net (losses) recoveries charged to allowance |  | 10 | 33 | (34) | (10) |
Credit loss expense |  | 563 | 16 | 748 | 4 |
Balance at the end of the period | 5,757 | 6,242 | 5,806 | 6,242 | 5,806 | 5,528
Real estate - mortgage | Domestic | Residential Junior Lien |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 10,077 | 10,648 | 10,031 | 11,024 | 11,024
Losses charged to allowance |  | (82) |  | (202) |  |
Recoveries credited to allowance |  | 109 | 26 | 116 | 35 |
Net (losses) recoveries charged to allowance |  | 27 | 26 | (86) | 35 |
Credit loss expense |  | (106) | (35) | 53 | (420) |
Balance at the end of the period | 10,648 | 9,998 | 10,639 | 9,998 | 10,639 | 10,031
Consumer | Domestic |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 262 | 313 | 281 | 318 | 318
Losses charged to allowance |  | (23) | (52) | (68) | (90) | (185)
Recoveries credited to allowance |  | 2 |  | 6 | 5 |
Net (losses) recoveries charged to allowance |  | (21) | (52) | (62) | (85) |
Credit loss expense |  | 32 | 53 | 54 | 81 |
Balance at the end of the period | 313 | 273 | 314 | 273 | 314 | 281
Foreign | Foreign |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward] |  |  |  |  |  |
Balance at the beginning of the period |  | 1,364 | 1,137 | 1,346 | 1,283 | 1,283
Credit loss expense |  | (33) | 202 | (15) | 56 |
Balance at the end of the period | $ 1,137 | $ 1,331 | $ 1,339 | $ 1,331 | $ 1,339 | $ 1,346

X
- Definition Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff due to bankruptcy of customer. + References No definition available. + Details
Name: | iboc_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffDueToBankruptcyOfCustomer
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 22 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-22 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=iboc_CommercialFinancialAndAgriculturalRealEstatePortfolioSegmentMember
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_GeographicDistributionAxis=us-gaap_GeographicDistributionDomesticMember
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: |