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v2.4.1.9

Allowance for Probable Loan Losses (Details 3) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | $ 63,559,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus | $ 62,823,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus | $ 71,768,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Reduced interest income on non-accrual loans | 4,013,000 iboc_FinancingReceivableRecordedInvestmentNonaccrualStatusReductionInInterestIncome | 4,088,000 iboc_FinancingReceivableRecordedInvestmentNonaccrualStatusReductionInInterestIncome | 2,549,000 iboc_FinancingReceivableRecordedInvestmentNonaccrualStatusReductionInInterestIncome
Accruing loans contractually past due 90 days or more as to principal or interest payments | 9,988,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing | 7,197,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing | 15,033,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Commercial |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 40,121,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialLoanMember | 34,110,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialLoanMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 2,890,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialLoanMember | 2,051,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialLoanMember |
Commercial real estate: other construction and land development |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 8,621,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateOtherConstructionAndLandDevelopmentReceivableMember | 11,726,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateOtherConstructionAndLandDevelopmentReceivableMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 439,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateOtherConstructionAndLandDevelopmentReceivableMember | 62,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateOtherConstructionAndLandDevelopmentReceivableMember |
Commercial real estate: farmland and commercial |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 11,903,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateFarmlandAndCommercialReceivableMember | 13,775,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateFarmlandAndCommercialReceivableMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 1,711,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateFarmlandAndCommercialReceivableMember | 417,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateFarmlandAndCommercialReceivableMember |
Commercial real estate: multifamily |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 835,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateMultifamilyReceivableMember | 295,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateMultifamilyReceivableMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 21,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_CommercialRealEstateMultifamilyReceivableMember |  |
Residential: first lien |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 527,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialFirstMortgageFinancingReceivableMember | 1,266,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialFirstMortgageFinancingReceivableMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 3,901,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialFirstMortgageFinancingReceivableMember | 3,518,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialFirstMortgageFinancingReceivableMember |
Residential: junior lien |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 1,523,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialSecondMortgageFinancingReceivableMember | 1,576,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialSecondMortgageFinancingReceivableMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | 431,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialSecondMortgageFinancingReceivableMember | 368,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = iboc_ResidentialSecondMortgageFinancingReceivableMember |
Consumer Loan |  |  |
Loan loss allowances, financing receivable past due |  |  |
Non-accrual loans, total | 29,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember | 75,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember |
Accruing loans contractually past due 90 days or more as to principal or interest payments | $ 482,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember | $ 781,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember |

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- Definition Recorded investment in financing receivables that are 90 days or more past due and still accruing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524 + Details
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- Definition Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524 + Details
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