XML 46 R35.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Allowance for Probable Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Mar. 31, 2016 | Dec. 31, 2016
Interest Recognized |  |  |
Total trouble debt restructuring | $ 21,708 |  | $ 22,418
Period of charge off for past due unsecured commercial loans | 90 days |  |
Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance | $ 3,516 |  | 4,828
Total impaired loans with no related allowance | 39,497 |  | 42,577
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded | 5,801 |  | 5,981
Total impaired loans with no related allowance recorded | 68,282 |  | 74,677
Related Allowance | 1,504 |  | 961
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded | 4,346 | $ 10,302 | 5,821
Total impaired loans with no related allowance recorded | 40,286 | 44,438 | 40,450
Interest Recognized |  |  |
Total impaired loans with an allowance recorded |  | 26 |
Total impaired loans with no related allowance recorded | 124 | 116 | 547
Commercial |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 10,113 |  | 10,710
Commercial | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance | 1,159 |  |
Total impaired loans with no related allowance | 20,177 |  | 21,412
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded | 2,288 |  |
Total impaired loans with no related allowance recorded | 47,901 |  | 50,737
Related Allowance | 278 |  |
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded | 1,165 | 4,017 |
Total impaired loans with no related allowance recorded | 20,789 | 21,051 | 19,354
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded | 1 | 1 | 3
Commercial Real Estate: Other Construction and Land Development | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance | 970 |  | 1,958
Total impaired loans with no related allowance | 2,617 |  | 2,818
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded | 986 |  | 1,971
Total impaired loans with no related allowance recorded | 2,705 |  | 4,419
Related Allowance | 319 |  | 371
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded | 1,299 | 165 | 2,512
Total impaired loans with no related allowance recorded | 2,683 | 6,296 | 2,336
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded |  | 25 | 67
Commercial Real Estate: Farmland & Commercial |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 3,055 |  | 3,086
Commercial Real Estate: Farmland & Commercial | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance | 1,325 |  | 2,808
Total impaired loans with no related allowance | 6,672 |  | 8,002
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded | 2,465 |  | 3,948
Total impaired loans with no related allowance recorded | 7,529 |  | 9,054
Related Allowance | 863 |  | 546
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded | 1,820 | 6,120 | 3,247
Total impaired loans with no related allowance recorded | 6,751 | 7,590 | 8,523
Interest Recognized |  |  |
Total impaired loans with an allowance recorded |  | 26 |
Total impaired loans with no related allowance recorded | 28 |  | 110
Commercial Real Estate: Multifamily | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance |  |  | 62
Total impaired loans with no related allowance | 532 |  | 552
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded |  |  | 62
Total impaired loans with no related allowance recorded | 547 |  | 562
Related Allowance |  |  | 44
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded |  |  | 62
Total impaired loans with no related allowance recorded | 539 | 168 | 401
Residential First Lien |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 6,166 |  | 6,181
Residential First Lien | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with related allowance | 62 |  |
Total impaired loans with no related allowance | 6,528 |  | 6,774
Unpaid principal balance: |  |  |
Total impaired loans with an allowance recorded | 62 |  |
Total impaired loans with no related allowance recorded | 6,605 |  | 6,847
Related Allowance | 44 |  |
Average recorded investment: |  |  |
Total impaired loans with an allowance recorded | 62 |  |
Total impaired loans with no related allowance recorded | 6,558 | 6,340 | 6,860
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded | 79 | 71 | 298
Residential Junior Lien |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 803 |  | 812
Residential Junior Lien | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with no related allowance | 968 |  | 978
Unpaid principal balance: |  |  |
Total impaired loans with no related allowance recorded | 992 |  | 1,017
Average recorded investment: |  |  |
Total impaired loans with no related allowance recorded | 972 | 1,036 | 1,011
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded | 12 | 15 | 52
Consumer |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 1,204 |  | 1,269
Consumer | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with no related allowance | 1,246 |  | 1,295
Unpaid principal balance: |  |  |
Total impaired loans with no related allowance recorded | 1,246 |  | 1,295
Average recorded investment: |  |  |
Total impaired loans with no related allowance recorded | 1,246 | 1,210 | 1,214
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded |  |  | 1
Foreign |  |  |
Interest Recognized |  |  |
Total trouble debt restructuring | 367 |  | 360
Foreign | Class of Financing Receivable |  |  |
Recorded investment: |  |  |
Total impaired loans with no related allowance | 757 |  | 746
Unpaid principal balance: |  |  |
Total impaired loans with no related allowance recorded | 757 |  | 746
Average recorded investment: |  |  |
Total impaired loans with no related allowance recorded | 748 | 747 | 751
Interest Recognized |  |  |
Total impaired loans with no related allowance recorded | $ 4 | $ 4 | $ 16

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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Recorded Investment -URI http://asc.fasb.org/extlink&oid=65880944 + 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 -Glossary Recorded Investment -URI http://asc.fasb.org/extlink&oid=65880944 Reference 2: 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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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=66008989&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: |