XML 40 R29.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Fair Value (Fair Value Measurement and Assumptions) (Details) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2016 | Jun. 30, 2016 | Dec. 31, 2015
Assets: |  |  |
Impaired Loans | $ 28,184,000 | $ 28,184,000 | $ 51,021,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Charges to allowance for probable loan losses in connection with other real estate owned | 149,000 | 381,000 |
Adjustment to fair value in connection with other real estate owned | 523,000 | 570,000 |
Impaired commercial collateral dependent loans | 28,184,000 | 28,184,000 | 51,021,000
Impaired commercial collateral dependent receivables appraisals to determine fair value within immediately preceding twelve months | 12,603,000 | 12,603,000 | 39,520,000
Impaired collateral dependent commercial loans with internal evaluation completed within last twelve months | $ 7,922,000 | $ 7,922,000 | $ 2,958,000
Significant Unobservable Inputs (Level 3) | Bond meeting original contract terms |  |  |
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Minimum period of residential mortgage loan performance under original contract terms |  | 24 months | 24 months
Estimated future principal prepayment rate assumption, low end of range (as a percent) | 7.00% | 7.00% | 7.00%
Default rate assumptions (as a percent) | 1.00% | 1.00% | 1.00%
Loss severity rate assumptions, first year (as a percent) | 25.00% | 25.00% | 25.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent) | 13.00% | 13.00% | 13.00%
Significant Unobservable Inputs (Level 3) | Bond not meeting the original contract terms |  |  |
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Estimated future principal prepayment rate assumption, low end of range (as a percent) | 2.00% | 2.00% | 2.00%
Default rate assumptions (as a percent) | 4.50% | 4.50% | 4.50%
Loss severity rate assumptions, first year (as a percent) | 60.00% | 60.00% | 60.00%
Decrease in loss severity rates, following five years (as a percent) |  | 5.00% | 5.00%
Loss severity rate, thereafter (as a percent) | 25.00% | 25.00% | 25.00%
Estimated future principal prepayment rate assumption, discount rate (as a percent) | 13.00% | 13.00% | 13.00%
Measured on a non-recurring basis |  |  |
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Change in net provision, impaired loans | $ 17,057,000 | $ 17,057,000 | $ (8,589,000)
Change in net provision, other real estate owned | 570,000 | 570,000 | 1,023,000
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) |  |  |
Assets: |  |  |
Impaired Loans | 34,468,000 | 34,468,000 | 18,033,000
Non-financial assets: |  |  |
Other real estate owned | 4,338,000 | 4,338,000 | 12,705,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Impaired commercial collateral dependent loans | 34,468,000 | 34,468,000 | 18,033,000
Measured on a non-recurring basis | Assets/liabilities measured at fair value |  |  |
Assets: |  |  |
Impaired Loans | 34,468,000 | 34,468,000 | 18,033,000
Non-financial assets: |  |  |
Other real estate owned | 4,338,000 | 4,338,000 | 12,705,000
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3 |  |  |
Impaired commercial collateral dependent loans | $ 34,468,000 | $ 34,468,000 | $ 18,033,000

X
- Definition Amount of increase (decrease) of allowance reserve for credit losses in connection with loans transferred to other real estate owned. + References No definition available. + Details
Name: | iboc_AllowanceForLoanAndLeaseLossesPeriodIncreaseDecreaseLoansTransferredToOtherRealEstateOwned
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reflects the amount of charge-off related to a loan prior to foreclosure. + References No definition available. + Details
Name: | iboc_AllowanceForLoanLeaseLossesWriteOffsPriorToForeclosure
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The estimated fair value of recorded investment related to change in provision for impaired financing receivables measured at fair value. + References No definition available. + Details
Name: | iboc_ChangeInProvisionOfImpairedFinancingReceivableFairValueDisclosure
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of change in Provision of other real estate and foreclosed assets. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings. + References No definition available. + Details
Name: | iboc_ChangeInProvisionOfOtherRealEstateAndForeclosedAssetsInUse
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The decline in the loss severity rate assumptions for the following five years used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsDeclineInLossSeverityRatesForFollowingFifthYear
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Default rate assumption used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsDefaultRates
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The discount rate assumption of estimated future principal prepayment rate assumption used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsFuturePrincipalPrepaymentDiscountRate
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The low end of range of estimated future principal prepayment rate assumption used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsFuturePrincipalPrepaymentRatesLowEndOfRange
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Loss severity rates assumption for the first year used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsLossSeverityRatesForFirstYear
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Loss severity rates assumption for the remaining years used in the discounted cash flow model for investments classified within level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelAssumptionsLossSeverityRatesThereafter
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The minimum period where the underlying residential mortgage loans must perform under original contract terms as a basis for certain discounted cash flow assumptions to be used. + References No definition available. + Details
Name: | iboc_FairValueMeasurementsDiscountedCashFlowModelMinimumPerformancePeriodUnderOriginalTerms
Namespace Prefix: | iboc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The impaired collateral dependent commercial loans where an internal evaluation has been done in the last twelve months. + References No definition available. + Details
Name: | iboc_ImpairedCollateralDependentCommercialLoansWithInternalEvaluationCompletedWithinLastTwelveMonths
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the impaired commercial collateral dependent financing receivables where the basis for fair value is an appraisal obtained in the last twelve months. + References No definition available. + Details
Name: | iboc_ImpairedCommercialCollateralFinancingReceivableAppraisalsToDetermineFairValue
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The estimated fair value of the recorded impaired collateral measured on a non-recurring basis as of the reporting date. + References No definition available. + Details
Name: | iboc_ImpairedFinancingReceivableRecordedInvestmentFairValueDisclosure
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of other real estate and foreclosed assets. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings. + References No definition available. + Details
Name: | iboc_OtherRealEstateAndForeclosedAssetsInUse
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=iboc_BondMeetingOriginalContractTermsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=iboc_BondNotMeetingOriginalContractTermsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |