XML 26 R35.htm IDEA: XBRL DOCUMENT
v3.19.3

Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Dec. 31, 2018
Interest Recognized |  |  |  |
Total trouble debt restructuring | $ 7,839 |  | $ 7,839 | $ 8,158
Period of charge off for past due unsecured commercial loans | 90 days |  | 90 days |
Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with related allowance | $ 726 | $ 1,936 | $ 726 | 1,698
Total impaired loans with no related allowance | 19,263 | 65,134 | 19,263 | 22,202
Unpaid principal balance: |  |  |  |
Total impaired loans with an allowance recorded | 790 |  | 790 | 2,330
Total impaired loans with no related allowance recorded | 20,480 | 276 | 20,480 | 23,284
Related Allowance | 511 |  | 511 | 772
Average recorded investment: |  |  |  |
Total impaired loans with an allowance recorded | 731 | 1,759 | 748 | 1,882
Total impaired loans with no related allowance recorded | 22,297 | 32,938 | 51,852 | 65,192
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded | 92 | 92 | 274 | 368
Commercial |  |  |  |
Interest Recognized |  |  |  |
Total trouble debt restructuring | 33 |  | 33 | 35
Commercial | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with related allowance | 598 | 1,794 | 598 | 1,563
Total impaired loans with no related allowance | 6,814 | 16,464 | 6,814 | 7,616
Unpaid principal balance: |  |  |  |
Total impaired loans with an allowance recorded | 621 |  | 621 | 2,161
Total impaired loans with no related allowance recorded | 6,963 | 2 | 6,963 | 7,730
Related Allowance | 395 |  | 395 | 656
Average recorded investment: |  |  |  |
Total impaired loans with an allowance recorded | 602 | 1,620 | 616 | 1,741
Total impaired loans with no related allowance recorded | 8,002 | 15,758 | 17,945 | 16,194
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded | 1 |  | 2 | 3
Commercial Real Estate:Other Construction and Land Development | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with related allowance | 128 | 142 | 128 | 135
Total impaired loans with no related allowance | 1,666 | 2,203 | 1,666 | 1,957
Unpaid principal balance: |  |  |  |
Total impaired loans with an allowance recorded | 169 |  | 169 | 169
Total impaired loans with no related allowance recorded | 1,953 |  | 1,953 | 2,205
Related Allowance | 116 |  | 116 | 116
Average recorded investment: |  |  |  |
Total impaired loans with an allowance recorded | 129 | 139 | 132 | 141
Total impaired loans with no related allowance recorded | 1,674 | 1,994 | 1,767 | 2,151
Commercial Real Estate: Farmland and Commercial | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 1,740 | 36,633 | 1,740 | 3,509
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 2,368 |  | 2,368 | 4,031
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 3,222 | 5,986 | 22,389 | 36,632
Commercial Real Estate: Multifamily | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 649 | 575 | 649 | 507
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 684 |  | 684 | 538
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 653 | 590 | 656 | 565
Residential First Lien |  |  |  |
Interest Recognized |  |  |  |
Total trouble debt restructuring | 5,703 |  | 5,703 | 5,947
Residential First Lien | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 6,286 | 6,929 | 6,286 | 6,244
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 6,400 | 228 | 6,400 | 6,386
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 6,427 | 6,362 | 6,698 | 7,136
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded | 78 | 76 | 231 | 305
Residential Junior Lien |  |  |  |
Interest Recognized |  |  |  |
Total trouble debt restructuring | 704 |  | 704 | 730
Residential Junior Lien | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 704 | 807 | 704 | 901
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 708 | 33 | 708 | 911
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 914 | 743 | 1,028 | 976
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded | 10 | 11 | 32 | 44
Consumer |  |  |  |
Interest Recognized |  |  |  |
Total trouble debt restructuring | 1,126 |  | 1,126 | 1,153
Consumer | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 1,131 | 1,192 | 1,131 | 1,175
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 1,131 | 2 | 1,131 | 1,190
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 1,131 | 1,187 | 1,088 | 1,211
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded |  | 1 |  | 2
Foreign |  |  |  |
Interest Recognized |  |  |  |
Total trouble debt restructuring | 273 |  | 273 | 293
Foreign | Class of Financing Receivable |  |  |  |
Recorded investment: |  |  |  |
Total impaired loans with no related allowance | 273 | 331 | 273 | 293
Unpaid principal balance: |  |  |  |
Total impaired loans with no related allowance recorded | 273 | 11 | 273 | 293
Average recorded investment: |  |  |  |
Total impaired loans with no related allowance recorded | 274 | 318 | 281 | 327
Interest Recognized |  |  |  |
Total impaired loans with no related allowance recorded | $ 3 | $ 4 | $ 9 | $ 14

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 http://asc.fasb.org/extlink&oid=118936363&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 http://asc.fasb.org/extlink&oid=118939409&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 http://asc.fasb.org/extlink&oid=119407570&loc=SL82919253-210447 + Details
Name: | us-gaap_FinancingReceivableThresholdPeriodPastDueWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableAverageRecordedInvestmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethodAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of allowance for credit losses related to recorded investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of investment in impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of investment in impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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: |