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Capital Requirements (Details 2) (USD $) In Thousands, unless otherwise specified | 0 Months Ended |  |
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Jan. 01, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets |
Forecast |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount | $ 500,000 us-gaap_Capital / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 4.50%us-gaap_CapitalToRiskWeightedAssets / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 2.50%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |
Term of mandatory compliance | 4 years |  |
Parent Company |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount |  | 1,524,998 us-gaap_Capital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,442,837 us-gaap_Capital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Tier 1 Capital (to Risk Weighted Assets), Actual Amount |  | 1,457,068 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,369,657 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Tier 1 Capital (to Average Assets), Actual Amount |  | 1,457,068 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,369,657 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 20.24%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 20.36%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 19.34%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 19.33%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent) |  | 12.33%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 11.61%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Parent Company | Minimum |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 602,847 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 566,870 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 301,424 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 283,435 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount |  | 472,864 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 472,044 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember
International Bank of Commerce, Laredo |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount |  | 1,131,528 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 1,035,189 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
Tier 1 Capital (to Risk Weighted Assets), Actual Amount |  | 1,071,360 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 969,731 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
Tier 1 Capital (to Average Assets), Actual Amount |  | 1,071,360 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 969,731 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 17.31%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 16.96%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 16.39%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 15.89%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent) |  | 11.22%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember | 10.09%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember
International Bank of Commerce, Laredo | Minimum |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 523,006 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 488,303 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 653,757 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 610,378 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 261,503 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 244,151 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 392,254 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 366,227 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount |  | 381,804 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 384,497 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 477,255 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 480,622 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceLaredoMember / us-gaap_RangeAxis = us-gaap_MinimumMember
International Bank of Commerce, Brownsville |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount |  | 151,489 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 143,879 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
Tier 1 Capital (to Risk Weighted Assets), Actual Amount |  | 145,584 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 138,467 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
Tier 1 Capital (to Average Assets), Actual Amount |  | 145,584 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 138,467 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 28.60%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 27.63%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 27.48%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 26.60%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent) |  | 13.96%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember | 13.33%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember
International Bank of Commerce, Brownsville | Minimum |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 42,381 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 41,652 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 52,976 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 52,065 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 21,190 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 20,826 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 31,785 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 31,239 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount |  | 41,717 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 41,553 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 52,146 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 51,942 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceBrownsvilleMember / us-gaap_RangeAxis = us-gaap_MinimumMember
International Bank of Commerce, Zapata |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount |  | 60,946 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 57,675 us-gaap_Capital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
Tier 1 Capital (to Risk Weighted Assets), Actual Amount |  | 60,035 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 56,459 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
Tier 1 Capital (to Average Assets), Actual Amount |  | 60,035 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 56,459 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 33.83%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 32.65%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 33.33%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 31.96%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent) |  | 10.88%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember | 10.64%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember
International Bank of Commerce, Zapata | Minimum |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 14,412 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 14,130 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 18,041 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 17,663 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 7,206 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 7,065 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 10,809 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10,598 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount |  | 22,081 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 21,219 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 27,602 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 26,523 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_InternationalBankOfCommerceZapataMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Commerce Bank |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), Actual Amount |  | 68,291 us-gaap_Capital / dei_LegalEntityAxis = iboc_CommerceBankMember | 64,585 us-gaap_Capital / dei_LegalEntityAxis = iboc_CommerceBankMember
Tier 1 Capital (to Risk Weighted Assets), Actual Amount |  | 67,347 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_CommerceBankMember | 63,491 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = iboc_CommerceBankMember
Tier 1 Capital (to Average Assets), Actual Amount |  | 67,347 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_CommerceBankMember | 63,491 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = iboc_CommerceBankMember
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 37.42%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember | 36.45%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember
Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) |  | 36.90%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember | 35.83%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember
Tier 1 Capital (to Average Assets), Actual Ratio (as a percent) |  | 12.04%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember | 11.88%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember
Commerce Bank | Minimum |  |  |
Capital Requirements |  |  |
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 14,600 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 14,175 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 18,251 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 17,719 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount |  | 7,300 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 7,087 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 10,950 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10,631 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount |  | 22,373 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 21,372 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount |  | 27,966 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | $ 26,715 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) |  | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = iboc_CommerceBankMember / us-gaap_RangeAxis = us-gaap_MinimumMember

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- Definition The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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