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Capital Requirements (Details)	12 Months Ended
	Dec. 31, 2024 USD ($)
Capital Requirements
Dividend payable by subsidiaries, maximum	$ 1,440,000,000

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