XML 48 R37.htm IDEA: XBRL DOCUMENT
v3.21.2

Allowance for Credit Losses (Portfolio Credit Quality) (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Loan portfolio by credit quality indicator |  |
2021 | $ 2,623,804 |
2020 | 2,065,068 | $ 3,601,680
2019 | 1,119,851 | 1,627,511
2018 | 821,429 | 1,087,031
2017 | 429,875 | 556,923
2016/Prior | 344,131 | 327,336
Prior |  | 341,273
Total loans | 7,404,158 | 7,541,754
Commercial, financial and agricultural |  |
Loan portfolio by credit quality indicator |  |
Total loans | 4,680,091 | 4,516,288
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 814,350 |
2020 | 473,912 | 1,288,332
2019 | 127,778 | 241,724
2018 | 104,877 | 146,051
2017 | 67,524 | 85,596
2016/Prior | 8,408 | 14,216
Prior |  | 10,017
Total loans | 1,596,849 | 1,785,936
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 775,702 |
2020 | 398,790 | 1,168,671
2019 | 126,858 | 240,869
2018 | 104,736 | 145,670
2017 | 67,433 | 85,434
2016/Prior | 8,398 | 13,901
Prior |  | 10,000
Total loans | 1,481,917 | 1,664,545
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] | Special Mention [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 1,517 |
2020 | 74,691 | 75,638
2019 | 139 |
2018 | 81 |
Total loans | 76,428 | 75,638
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] | Special Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 33,793 |
2020 |  | 39,886
2019 |  | 11
2017 |  | 3
2016/Prior | 10 |
Prior |  | 17
Total loans | 33,803 | 39,917
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] | Substandard [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 3,232 |
2020 | 297 | 3,360
2019 | 781 | 683
2018 | 60 | 289
2016/Prior |  | 315
Total loans | 4,370 | 4,647
Commercial, financial and agricultural | Domestic | Commercial Loan [Member] | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2021 | 106 |
2020 | 134 | 777
2019 |  | 161
2018 |  | 92
2017 | 91 | 159
Total loans | 331 | 1,189
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 793,540 |
2020 | 799,495 | 1,002,557
2019 | 331,449 | 380,123
2018 | 459,516 | 391,303
2017 | 199,665 | 192,165
2016/Prior | 132,412 | 206,193
Prior |  | 116,967
Total loans | 2,716,077 | 2,289,308
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 771,884 |
2020 | 699,685 | 884,070
2019 | 326,176 | 373,993
2018 | 455,899 | 386,268
2017 | 197,313 | 189,639
2016/Prior | 131,756 | 202,500
Prior |  | 116,729
Total loans | 2,582,713 | 2,153,199
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] | Special Mention [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 2,849 |
2020 | 1,314 | 3,041
2019 | 910 |
2018 | 3,617 | 4,758
2017 | 63 | 177
2016/Prior | 194 | 3,218
Total loans | 8,947 | 11,194
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] | Special Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 17,503 |
2020 | 44,143 | 61,637
2019 |  | 942
2018 |  | 277
2017 | 94 | 80
2016/Prior | 1 |
Total loans | 61,741 | 62,936
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] | Substandard [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 1,304 |
2020 | 54,124 | 53,809
2019 | 4,178 | 4,986
2017 | 2,195 | 2,269
2016/Prior | 461 | 475
Prior |  | 1
Total loans | 62,262 | 61,540
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member] | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2020 | 229 |
2019 | 185 | 202
Prior |  | 237
Total loans | 414 | 439
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 40,569 |
2020 | 81,244 | 74,711
2019 | 98,720 | 208,356
2018 | 76,109 | 82,818
2017 | 63,220 | 64,110
2016/Prior | 7,303 | 6,801
Prior |  | 4,248
Total loans | 367,165 | 441,044
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member] | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 40,569 |
2020 | 81,107 | 74,577
2019 | 98,720 | 208,356
2018 | 76,109 | 82,818
2017 | 63,220 | 64,110
2016/Prior | 7,303 | 6,801
Prior |  | 4,248
Total loans | 367,028 | 440,910
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member] | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2020 | 137 | 134
Total loans | 137 | 134
Commercial Real Estate Portfolio Segment [Member] |  |
Loan portfolio by credit quality indicator |  |
Total loans | 1,671,212 | 1,846,757
Commercial Real Estate Portfolio Segment [Member] | Domestic | Commercial Real Estate: other construction and land development |  |
Loan portfolio by credit quality indicator |  |
2021 | 689,447 |
2020 | 464,541 | 833,796
2019 | 414,067 | 600,602
2018 | 83,925 | 320,308
2017 | 15,826 | 78,174
2016/Prior | 3,406 | 10,534
Prior |  | 3,343
Total loans | 1,671,212 | 1,846,757
Commercial Real Estate Portfolio Segment [Member] | Domestic | Commercial Real Estate: other construction and land development | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 657,381 |
2020 | 441,333 | 773,165
2019 | 413,856 | 576,707
2018 | 83,925 | 320,308
2017 | 15,826 | 78,174
2016/Prior | 3,406 | 10,534
Prior |  | 3,343
Total loans | 1,615,727 | 1,762,231
Commercial Real Estate Portfolio Segment [Member] | Domestic | Commercial Real Estate: other construction and land development | Special Mention [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 31,527 |
2020 |  | 20,828
2019 | 211 | 21,650
Total loans | 31,738 | 42,478
Commercial Real Estate Portfolio Segment [Member] | Domestic | Commercial Real Estate: other construction and land development | Special Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2020 | 23,101 | 23,101
2019 |  | 1,451
Total loans | 23,101 | 24,552
Commercial Real Estate Portfolio Segment [Member] | Domestic | Commercial Real Estate: other construction and land development | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2021 | 539 |
2020 | 107 | 16,702
2019 |  | 794
Total loans | 646 | 17,496
Real estate - mortgage |  |
Loan portfolio by credit quality indicator |  |
Total loans | 876,313 | 999,144
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 85,820 |
2020 | 56,776 | 81,090
2019 | 65,634 | 62,179
2018 | 51,959 | 72,430
2017 | 31,832 | 54,593
2016/Prior | 93,612 | 29,299
Prior |  | 105,528
Total loans | 385,633 | 405,119
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 85,763 |
2020 | 56,687 | 81,004
2019 | 65,531 | 62,165
2018 | 51,959 | 72,299
2017 | 31,709 | 54,593
2016/Prior | 93,611 | 29,250
Prior |  | 105,463
Total loans | 385,260 | 404,774
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] | Special Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2019 |  | 14
2018 |  | 131
Total loans |  | 145
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] | Substandard [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 57 |
2019 | 103 |
2017 | 123 |
2016/Prior | 1 | 49
Total loans | 284 | 49
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member] | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2020 | 89 | 86
Prior |  | 65
Total loans | 89 | 151
Real estate - mortgage | Domestic | Residential Junior Lien |  |
Loan portfolio by credit quality indicator |  |
2021 | 103,570 |
2020 | 141,401 | 197,048
2019 | 71,211 | 108,276
2018 | 35,364 | 61,674
2017 | 46,503 | 75,868
2016/Prior | 92,631 | 56,705
Prior |  | 94,454
Total loans | 490,680 | 594,025
Real estate - mortgage | Domestic | Residential Junior Lien | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 103,570 |
2020 | 141,368 | 196,308
2019 | 71,211 | 108,276
2018 | 35,364 | 61,636
2017 | 46,503 | 75,056
2016/Prior | 92,631 | 56,705
Prior |  | 94,454
Total loans | 490,647 | 592,435
Real estate - mortgage | Domestic | Residential Junior Lien | Special Mention [Member] |  |
Loan portfolio by credit quality indicator |  |
2020 |  | 740
2017 |  | 812
Total loans |  | 1,552
Real estate - mortgage | Domestic | Residential Junior Lien | Watch List - Doubtful |  |
Loan portfolio by credit quality indicator |  |
2020 | 33 |
2018 |  | 38
Total loans | 33 | 38
Consumer |  |
Loan portfolio by credit quality indicator |  |
Total loans | 40,699 | 40,595
Consumer | Domestic |  |
Loan portfolio by credit quality indicator |  |
2021 | 26,613 |
2020 | 10,196 | 30,910
2019 | 1,910 | 7,159
2018 | 332 | 875
2017 | 67 | 225
2016/Prior | 1,581 | 55
Prior |  | 1,371
Total loans | 40,699 | 40,595
Consumer | Domestic | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 26,613 |
2020 | 10,196 | 30,910
2019 | 1,910 | 7,159
2018 | 332 | 875
2017 | 67 | 225
2016/Prior | 1,581 | 55
Prior |  | 1,371
Total loans | 40,699 | 40,595
Foreign. |  |
Loan portfolio by credit quality indicator |  |
Total loans | 135,843 | 138,970
Foreign. | Foreign |  |
Loan portfolio by credit quality indicator |  |
2021 | 69,895 |
2020 | 37,503 | 93,236
2019 | 9,082 | 19,092
2018 | 9,347 | 11,572
2017 | 5,238 | 6,192
2016/Prior | 4,778 | 3,533
Prior |  | 5,345
Total loans | 135,843 | 138,970
Foreign. | Foreign | Pass [Member] |  |
Loan portfolio by credit quality indicator |  |
2021 | 69,895 |
2020 | 37,503 | 93,236
2019 | 9,082 | 19,092
2018 | 9,347 | 11,572
2017 | 5,238 | 6,192
2016/Prior | 4,778 | 3,533
Prior |  | 5,345
Total loans | $ 135,843 | $ 138,970

X
- Definition Amount of financing receivable originated more than six years prior to current fiscal year. + References No definition available. + Details
Name: | iboc_FinancingReceivableOriginatedMoreThanSixYearsBeforeCurrentFiscalYear
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated more than five years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated four years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in fiscal year prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 + Details
Name: | us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated three years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated two years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, before allowance for credit loss, of financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 80 -URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922355-210448 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (1) Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (2) Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher SEC -Name Regulation S-K (SK) -Number 229 -Section 1404 -Paragraph (a) + Details
Name: | us-gaap_NotesReceivableGross
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_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_DoubtfulMember
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: |