XML 34 R87.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Financial Instruments with Off-Statement of Condition Risk and Concentrations of Credit Risk (Details) (USD $) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2011 Maximum Y | Dec. 31, 2011 Commitments to extend credit | Dec. 31, 2011 Credit card lines | Dec. 31, 2011 Standby letters of credit | Dec. 31, 2011 Commercial letters of credit | Dec. 31, 2011 Unsecured letters of credit | Dec. 31, 2010 Unsecured letters of credit
Financial amounts of instruments, whose contract amounts represent credit risks |  |  |  |  |  |  |
Outstanding amount of financial instruments whose, contract amounts represent credit risks |  | $ 1,042,237,000 | $ 60,895,000 | $ 112,343,000 | $ 20,224,000 |  |
Unsecured letters of credit |  |  |  |  |  | $ 27,991,000 | $ 29,160,000
Credit risk commitment, maximum expiration date (in years) | 1 |  |  |  |  |  |

X
- Definition Represents the maximum fixed expiration date upon which commitments are set to expire. + References No definition available. + Details
Name: | iboc_CreditRiskCommitmentsExpirationDate
Namespace Prefix: | iboc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611 + Details
Name: | us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueOffBalanceSheetRisksDisclosureInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant