XML 101 R85.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Capital Requirements (Capital Amounts and Ratios) (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Parent Company |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 2,563,130 | $ 2,232,723
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2172% | 0.2021%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 2,790,171 | $ 2,455,468
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2365 | 0.2222
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 2,642,492 | $ 2,324,903
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2239 | 0.2104
Tier 1 Capital (to Average Assets), Actual Amount | $ 2,642,492 | $ 2,324,903
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1746 | 0.1459
Parent Company | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 825,968 | $ 773,398
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 1,238,952 | $ 1,160,096
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 1,002,961 | $ 939,126
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 605,262 | $ 637,578
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
International Bank of Commerce Laredo |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 1,444,775 | $ 1,310,616
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.1854% | 0.1807%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 1,542,462 | $ 1,401,298
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.1979 | 0.1932
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 1,444,775 | $ 1,310,616
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.1854 | 0.1807
Tier 1 Capital (to Average Assets), Actual Amount | $ 1,444,775 | $ 1,310,616
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1640 | 0.1309
International Bank of Commerce Laredo | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 545,611 | $ 507,625
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 506,639 | $ 471,366
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.065% | 0.065%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 818,416 | $ 761,438
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 779,444 | $ 725,179
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.1000 | 0.1000
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 662,527 | $ 616,402
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 623,555 | $ 580,143
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0800 | 0.0800
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 352,412 | $ 400,489
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 440,515 | $ 500,611
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0500 | 0.0500
International Bank of Commerce Brownsville |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 477,390 | $ 232,689
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2441% | 0.2117%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 500,268 | $ 243,739
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2558 | 0.2218
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 477,390 | $ 232,689
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2441 | 0.2117
Tier 1 Capital (to Average Assets), Actual Amount | $ 477,390 | $ 232,689
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1179 | 0.1348
International Bank of Commerce Brownsville | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 136,883 | $ 76,941
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 127,106 | $ 71,445
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.065% | 0.065%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 205,325 | $ 115,412
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 195,547 | $ 109,916
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.1000 | 0.1000
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 166,215 | $ 93,429
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 156,438 | $ 87,933
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0800 | 0.0800
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 161,919 | $ 69,028
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 202,398 | $ 86,286
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0500 | 0.0500
International Bank Of Commerce Oklahoma |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 232,965 | $ 363,093
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2072% | 0.2086%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 247,031 | $ 383,804
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2197 | 0.2205
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 232,965 | $ 363,093
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.2072 | 0.2086
Tier 1 Capital (to Average Assets), Actual Amount | $ 232,965 | $ 363,093
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1472 | 0.0895
International Bank Of Commerce Oklahoma | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 78,718 | $ 121,855
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 73,095 | $ 113,151
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.065% | 0.065%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 118,076 | $ 182,782
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 112,454 | $ 174,078
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.1000 | 0.1000
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 95,586 | $ 147,966
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 89,963 | $ 139,262
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0800 | 0.0800
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 63,294 | $ 162,246
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 79,117 | $ 202,808
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0500 | 0.0500
Commerce Bank |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 97,334 | $ 71,418
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3657% | 0.377%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 100,660 |
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3782 | 0.3876
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 97,334 | $ 73,420
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3657 | 0.3770
Tier 1 Capital (to Average Assets), Actual Amount | $ 97,334 | $ 71,418
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1450 | 0.1500
Commerce Bank | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 18,628 | $ 13,261
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 17,298 | $ 12,314
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.065% | 0.065%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 27,943 | $ 19,892
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 26,612 | $ 18,945
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.1000 | 0.1000
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 22,620 | $ 16,103
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 21,290 | $ 15,156
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0800 | 0.0800
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 26,858 | $ 19,048
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 33,572 | $ 23,811
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0500 | 0.0500
International Bank of Commerce Zapata |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 64,110 | $ 98,087
Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3118% | 0.4226%
Total Capital (to Risk Weighted Assets), Actual Amount | $ 66,680 | $ 100,798
Total Capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3243 | 0.4343
Tier 1 Capital (to Risk Weighted Assets), Actual Amount | $ 64,110 | $ 98,087
Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent) | 0.3118 | 0.4226
Tier 1 Capital (to Average Assets), Actual Amount | $ 64,110 | $ 98,087
Tier 1 capital (to Average Assets), Actual Ratio (as a percent) | 0.1326 | 0.1439
International Bank of Commerce Zapata | Minimum |  |
Capital Requirements |  |
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 14,394 | $ 16,248
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 13,366 | $ 15,088
Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.07% | 0.07%
Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.065% | 0.065%
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 21,591 | $ 24,372
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 20,563 | $ 23,212
Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.10500 | 0.10500
Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.1000 | 0.1000
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Amount | $ 17,478 | $ 19,730
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 16,450 | $ 18,569
Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.08500 | 0.08500
Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0800 | 0.0800
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Amount | $ 19,338 | $ 27,270
Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions Amount | $ 24,172 | $ 34,088
Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes Ratio (as a percent) | 0.0400 | 0.0400
Tier 1 Capital (to Average Assets), To Be well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent) | 0.0500 | 0.0500

X
- Definition Percentage of minimum common equity Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | iboc_CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | iboc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of Common Equity Tier 1 capital ratio (Common Equity Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References No definition available. + Details
Name: | iboc_CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | iboc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Common Equity Tier 1 capital (to Risk Weighted Assets), Actual Ratio (as a percent). + References No definition available. + Details
Name: | iboc_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix: | iboc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of minimum Tier 1 risk-based capital required for capital adequacy with capital conservation buffer, as defined by regulatory framework. + References No definition available. + Details
Name: | iboc_TierOneRiskBasedCapitalRequiredForCapitalAdequacyWithCapitalConservationBuffer
Namespace Prefix: | iboc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum Tier 1 risk-based capital to risk-weighted assets required for capital adequacy with capital conservation buffer, as defined by regulatory framework. + References No definition available. + Details
Name: | iboc_TierOneRiskBasedCapitalRequiredForCapitalAdequacyWithCapitalConservationBufferToRiskWeightedAssets
Namespace Prefix: | iboc_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of total capital as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_Capital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_CapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of minimum total risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_CapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum total risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ratio of total risk-based capital to risk-weighted assets as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of Common Equity Tier 1 risk-based capital as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_CommonEquityTierOneCapital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of minimum Common Equity Tier 1 risk-based capital required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_CommonEquityTierOneCapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of minimum Common Equity Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_CommonEquityTierOneCapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of Tier 1 leverage capital as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneLeverageCapital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of minimum Tier 1 leverage capital required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum Tier 1 leverage capital to average assets required for capital adequacy as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1B + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of minimum Tier 1 leverage capital categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum Tier 1 leverage capital to average assets categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ratio of Tier 1 capital to average assets as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of Tier 1 risk-based capital as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneRiskBasedCapital
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of minimum Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Ratio of minimum Tier 1 risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ratio of Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 505 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480696/942-505-50-1 + Details
Name: | us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=iboc_InternationalBankOfCommerceLaredoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=iboc_InternationalBankOfCommerceBrownsvilleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=iboc_InternationalBankOfCommerceOklahomaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=iboc_CommerceBankMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=iboc_InternationalBankOfCommerceZapataMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |