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Commitments, Contingent Liabilities and Other Tax Matters (Details) | Dec. 31, 2019 USD ($)
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Commitments and Contingent Liabilities and Other Matters, details |
Approximate cash maintained to satisfy regulatory reserve requirements | $ 125,764,000

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- Definition Represents the amount of cash maintained to satisfy regulatory reserve requirements as of the balance sheet date. + References No definition available. + Details
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Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration