XML 71 R56.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Summary of Significant Accounting Policies (Details) |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Oct. 01, 2018 USD ($) | Jun. 30, 2018 USD ($) | Dec. 31, 2018 USD ($) item | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Number of insurance-related subsidiaries | item |  |  | 1 |  |
Investment Securities |  |  |  |  |
Number of components in which other-than-temporary impairment is segregated | item |  |  | 2 |  |
Non-Accrual Loans |  |  |  |  |
Period of charge off for past due unsecured consumer loans |  |  | 90 days |  |
Minimum period that past due unsecured loans outstanding may not be placed on nonaccrual status under special circumstances |  |  | 90 days |  |
Maximum period of non-consumer loans outstanding that is used to evaluate whether loans should be placed on non-accrual status |  |  | 90 days |  |
Other Real Estate Owned and Reposessed Assets |  |  |  |  |
Other real estate owned |  |  | $ 57,344,000 | $ 30,519,000 |
Reposessed assets |  |  | $ 6,454,000 | 303,000 |
Income Taxes |  |  |  |  |
Percentage of likelihood of realization of recognized tax benefit |  |  | 50.00% |  |
Liability for unrecognized tax benefits |  |  | $ 0 | 0 |
Interest expense related to uncertain tax positions |  |  | 0 | 0 | $ 0
Penalties related to uncertain tax positions |  |  | 0 | $ 0 | $ 0
Goodwill and Identified Intangible Assets |  |  |  |  |
Goodwill impairment loss | $ 0 |  |  |  |
Impairment of identified intangible assets |  |  | $ 0 |  |
Segments of an Enterprise and Related Information |  |  |  |  |
Number of operating segments | item |  |  | 1 |  |
Number of active operating bank subsidiaries | item |  |  | 5 |  |
New Accounting Standards |  |  |  |  |
One-time reclassification from AOCI to retained earnings, relating to the Tax Cuts and Jobs Act of 2017 |  | $ 5,997,000 |  |  |
Equity securities with readily determinable fair values |  |  |  |  |
New Accounting Standards |  |  |  |  |
Net unrealized loss on available-for-sale equity securities |  |  | $ 189,000 |  |

X
- Definition Represents the number of insurance-related subsidiaries owned by the entity. + References No definition available. + Details
Name: | iboc_EntityNumberOfInsuranceRelatedSubsidiaries
Namespace Prefix: | iboc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

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

X
- Definition Represents the maximum period of non-consumer loans outstanding that is used to evaluate whether loans should be placed on non-accrual status. + References No definition available. + Details
Name: | iboc_MaximumPeriodOutstandingNonConsumerLoansAreEvaluatedForNonAccrualStatus
Namespace Prefix: | iboc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the minimum period that past due unsecured loans outstanding may not be placed on nonaccrual status under special circumstances. + References No definition available. + Details
Name: | iboc_MinimumPeriodForPastDueUnsecuredLoansOutstandingNotPlacedOnNonAccrualStatusUnderSpecialCircumstances
Namespace Prefix: | iboc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Represents the number of active operating subsidiaries of the entity. + References No definition available. + Details
Name: | iboc_NumberOfActiveOperatingSubsidiaries
Namespace Prefix: | iboc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of components in which other-than-temporary impairments are segregated. + References No definition available. + Details
Name: | iboc_NumberOfComponentsOtherThanTemporaryImpairmentSegregated
Namespace Prefix: | iboc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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
- Definition Represents the percentage of likelihood of realization of recognized benefit. + References No definition available. + Details
Name: | iboc_PercentageOfLikelihoodOfRealizationOfRecognizedTaxBenefit
Namespace Prefix: | iboc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period of charge off for past due unsecured commercial loans. + References No definition available. + Details
Name: | iboc_PeriodOfChargeOffForPastDueUnsecuredCommercialLoans
Namespace Prefix: | iboc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act of 2017. + References No definition available. + Details
Name: | iboc_TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13854-109267 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266 + Details
Name: | us-gaap_GoodwillImpairmentLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
Name: | us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

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

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
Name: | us-gaap_NumberOfOperatingSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of assets other than real property that were received in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5162-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4437-111522 + Details
Name: | us-gaap_OtherForeclosedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 10B -URI http://asc.fasb.org/extlink&oid=84176650&loc=SL37586934-109318 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense for penalties related to a tax position claimed or expected to be claimed in the tax return. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest expense for an underpayment of income taxes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |