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v3.25.4

Capital Requirements (Details) | 12 Months Ended
--- | ---
Dec. 31, 2025 USD ($)
Capital Requirements |
Dividend payable by subsidiaries, maximum | $ 1,644,000,000

X
- Definition Represents the maximum amount of dividend the subsidiary banks could pay to the entity. + References No definition available. + Details
Name: | iboc_MaximumDividendIncomeToBeReceivedFromSubsidiaries
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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