XML 40 R29.htm IDEA: XBRL DOCUMENT v3.21.1

Fair Value Measurements (Fair Value Measurement and Assumptions) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Assets:
Impaired Loans	$ 1,869,000	$ 18,361,000
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	0	22,000
Adjustment to fair value in connection with other real estate owned	150,000	1,539,000
Impaired commercial collateral dependent receivables appraisals to determine fair value within immediately preceding twelve months	468,000	16,587,000
Impaired collateral dependent commercial loans with internal evaluation completed within last twelve months	1,207,000	1,283,000
Fair Value, Measurements, Nonrecurring [Member]
Assumptions used in discounted cash flow model to determine fair value of investments classified within level 3
Change in net provision, impaired loans		(86,000)
Change in net provision, other real estate owned	150,000	1,539,000
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Watch-List doubtful loans		393,000
Non-financial assets:
Other real estate owned	1,184,000	6,241,000
Fair Value, Measurements, Nonrecurring [Member] | Estimate of Fair Value Measurement [Member]
Assets:
Watch-List doubtful loans		393,000
Non-financial assets:
Other real estate owned	$ 1,184,000	$ 6,241,000

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 estimated fair value of the watch-list doubtful loans measured on a non-recurring basis as of the reporting date.

+ References

No definition available.

+ Details

Name:	iboc_FinancingReceivableWatchListDoubtfulLoansRecordedInvestmentFairValueDisclosure
Namespace Prefix:	iboc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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_FairValueInputsQuantitativeInformationAbstract
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_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
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: