XML 42 R31.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Allowance for Probable Loan Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | $ 32,492 | $ 63,204
Loans Individually Evaluated for Impairment, Allowance | 700 | 434
Loans Collectively Evaluated for Impairment, Recorded Investment | 6,442,649 | 6,284,968
Loans Collectively Evaluated for Impairment, Allowance | 59,954 | 67,253
Commercial |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 17,236 | 17,947
Loans Individually Evaluated for Impairment, Allowance | 584 | 300
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,061,329 | 1,068,520
Loans Collectively Evaluated for Impairment, Allowance | 12,742 | 27,605
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 | 2,130 | 2,455
Loans Individually Evaluated for Impairment, Allowance | 116 | 116
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,876,310 | 1,681,095
Loans Collectively Evaluated for Impairment, Allowance | 14,988 | 11,559
Commercial Real Estate: Farmland and Commercial |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 4,157 | 33,123
Loans Individually Evaluated for Impairment, Allowance |  | 18
Loans Collectively Evaluated for Impairment, Recorded Investment | 1,977,397 | 2,010,162
Loans Collectively Evaluated for Impairment, Allowance | 19,365 | 16,645
Commercial Real Estate: Multifamily |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 586 | 476
Loans Collectively Evaluated for Impairment, Recorded Investment | 186,759 | 192,440
Loans Collectively Evaluated for Impairment, Allowance | 1,436 | 1,109
Residential First Lien |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 6,173 | 6,852
Loans Collectively Evaluated for Impairment, Recorded Investment | 420,373 | 425,925
Loans Collectively Evaluated for Impairment, Allowance | 3,186 | 2,950
Residential Junior Lien |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 740 | 723
Loans Collectively Evaluated for Impairment, Recorded Investment | 720,346 | 700,025
Loans Collectively Evaluated for Impairment, Allowance | 6,907 | 6,103
Consumer |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 1,164 | 1,281
Loans Collectively Evaluated for Impairment, Recorded Investment | 45,482 | 48,262
Loans Collectively Evaluated for Impairment, Allowance | 439 | 440
Foreign |  |
Loan loss allowances, impaired financing receivable, evaluated individually or collectively |  |
Loans Individually Evaluated for Impairment, Recorded Investment | 306 | 347
Loans Collectively Evaluated for Impairment, Recorded Investment | 154,653 | 158,539
Loans Collectively Evaluated for Impairment, Allowance | $ 891 | $ 842

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=84173941&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=84173941&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=84173941&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=84173941&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_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: |