XML 46 R35.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2016 | Dec. 31, 2015
Interest Recognized |  |
Total trouble debt restructuring | $ 16,070 | $ 15,719
Period of charge off for past due unsecured commercial loans | 90 days |
Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with related allowance | $ 10,299 | 8,785
Total impaired loans with no related allowance | 33,673 | 51,663
Unpaid principal balance: |  |
Total impaired loans with an allowance recorded | 10,532 | 9,233
Total impaired loans with no related allowance recorded | 61,983 | 64,788
Related Allowance | 3,723 | 2,206
Average recorded investment: |  |
Total impaired loans with an allowance recorded | 10,302 | 9,694
Total impaired loans with no related allowance recorded | 44,438 | 53,575
Interest Recognized |  |
Total impaired loans with an allowance recorded | 26 | 92
Total impaired loans with no related allowance recorded | 116 | 441
Commercial |  |
Interest Recognized |  |
Total trouble debt restructuring | 2,419 | 2,419
Commercial | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with related allowance | 4,018 | 4,016
Total impaired loans with no related allowance | 10,840 | 26,930
Unpaid principal balance: |  |
Total impaired loans with an allowance recorded | 4,158 | 4,156
Total impaired loans with no related allowance recorded | 37,845 | 38,845
Related Allowance | 2,347 | 1,704
Average recorded investment: |  |
Total impaired loans with an allowance recorded | 4,017 | 3,758
Total impaired loans with no related allowance recorded | 21,051 | 30,847
Interest Recognized |  |
Total impaired loans with no related allowance recorded | 1 | 4
Commercial Real Estate: Other Construction and Land Development |  |
Interest Recognized |  |
Total trouble debt restructuring | 2,553 | 2,553
Commercial Real Estate: Other Construction and Land Development | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with related allowance | 165 | 167
Total impaired loans with no related allowance | 5,800 | 6,054
Unpaid principal balance: |  |
Total impaired loans with an allowance recorded | 169 | 169
Total impaired loans with no related allowance recorded | 5,801 | 6,204
Related Allowance | 116 | 100
Average recorded investment: |  |
Total impaired loans with an allowance recorded | 165 | 893
Total impaired loans with no related allowance recorded | 6,296 | 6,455
Interest Recognized |  |
Total impaired loans with no related allowance recorded | 25 | 85
Commercial Real Estate: Farmland & Commercial |  |
Interest Recognized |  |
Total trouble debt restructuring | 2,847 | 2,853
Commercial Real Estate: Farmland & Commercial | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with related allowance | 6,116 | 4,003
Total impaired loans with no related allowance | 7,524 | 9,803
Unpaid principal balance: |  |
Total impaired loans with an allowance recorded | 6,205 | 4,309
Total impaired loans with no related allowance recorded | 8,730 | 10,717
Related Allowance | 1,260 | 202
Average recorded investment: |  |
Total impaired loans with an allowance recorded | 6,120 | 4,444
Total impaired loans with no related allowance recorded | 7,590 | 7,258
Interest Recognized |  |
Total impaired loans with an allowance recorded | 26 | 92
Commercial Real Estate: Multifamily | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with related allowance |  | 599
Total impaired loans with no related allowance | 164 | 178
Unpaid principal balance: |  |
Total impaired loans with an allowance recorded |  | 599
Total impaired loans with no related allowance recorded | 164 | 178
Related Allowance |  | 200
Average recorded investment: |  |
Total impaired loans with an allowance recorded |  | 599
Total impaired loans with no related allowance recorded | 168 | 205
Residential First Lien |  |
Interest Recognized |  |
Total trouble debt restructuring | 5,709 | 5,316
Residential First Lien | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with no related allowance | 6,358 | 5,699
Unpaid principal balance: |  |
Total impaired loans with no related allowance recorded | 6,433 | 5,822
Average recorded investment: |  |
Total impaired loans with no related allowance recorded | 6,340 | 5,853
Interest Recognized |  |
Total impaired loans with no related allowance recorded | 71 | 264
Residential Junior Lien |  |
Interest Recognized |  |
Total trouble debt restructuring | 988 | 929
Residential Junior Lien | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with no related allowance | 1,032 | 950
Unpaid principal balance: |  |
Total impaired loans with no related allowance recorded | 1,055 | 972
Average recorded investment: |  |
Total impaired loans with no related allowance recorded | 1,036 | 1,182
Interest Recognized |  |
Total impaired loans with no related allowance recorded | 15 | 68
Consumer |  |
Interest Recognized |  |
Total trouble debt restructuring | 1,174 | 1,263
Consumer | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with no related allowance | 1,210 | 1,297
Unpaid principal balance: |  |
Total impaired loans with no related allowance recorded | 1,210 | 1,298
Average recorded investment: |  |
Total impaired loans with no related allowance recorded | 1,210 | 1,227
Interest Recognized |  |
Total impaired loans with no related allowance recorded |  | 3
Foreign |  |
Interest Recognized |  |
Total trouble debt restructuring | 380 | 386
Foreign | Class of Financing Receivable |  |
Recorded investment: |  |
Total impaired loans with no related allowance | 745 | 752
Unpaid principal balance: |  |
Total impaired loans with no related allowance recorded | 745 | 752
Average recorded investment: |  |
Total impaired loans with no related allowance recorded | 747 | 548
Interest Recognized |  |
Total impaired loans with no related allowance recorded | $ 4 | $ 17

X
- Definition The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554 + Details
Name: | us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=49124121&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 interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
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 a related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=49124121&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_ThresholdPeriodPastDueForWriteoffOfFinancingReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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: |