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Capital and Regulatory Matters - Actual and Required Capital Ratios (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Cullen/Frost [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount | $ 1,957,452 cfr_CommonEquityTierOneCapital / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio | 11.55%cfr_ExcessCommonEquityTierOneCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 762,847 cfr_CommonEquityTierOneCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 4.50%cfr_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,186,195 cfr_CommonEquityTierOneCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio | 7.00%cfr_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount | 1,101,890 cfr_CommonEquityTierOneCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember |
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Ratio | 6.50%cfr_CommonEquityTierOneCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember |
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount | 2,135,188 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = cfr_CullenFrostMember | 2,186,276 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = cfr_CullenFrostMember
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio | 12.60%us-gaap_ExcessTierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 13.68%us-gaap_ExcessTierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,017,129 cfr_TierOneRiskBasedCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 6.00%cfr_TierOneRiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,440,379 cfr_TierOneRiskBasedCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 8.50%cfr_TierOneRiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount | 1,356,172 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember | 959,098 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Actual, Capital Amount | 2,360,646 us-gaap_Capital / dei_LegalEntityAxis = cfr_CullenFrostMember | 2,325,818 us-gaap_Capital / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Actual, Ratio | 13.93%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 14.55%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,356,172 cfr_CapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase - In Schedule, Ratio | 8.00%cfr_CapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,779,292 cfr_CapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 10.50%cfr_CapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount | 1,695,215 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember | 1,598,496 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Actual, Capital Amount | 2,135,188 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = cfr_CullenFrostMember | 2,186,276 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Actual, Ratio | 7.89%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 8.16%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,083,075 cfr_TierOneLeverageCapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Leverage Ratio, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 4.00%cfr_TierOneLeverageCapitalRequiredforCapitalAdequacytoAverageAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_CullenFrostMember |
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,082,814 cfr_TierOneLeverageCapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 4.00%cfr_TierOneLeverageCapitalRequiredforCapitalAdequacytoAverageAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_CullenFrostMember |
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount | 1,353,843 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember | 1,340,043 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Required to be Considered Well Capitalized, Ratio | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = cfr_CullenFrostMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Capital Amount |  | 639,398 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_CullenFrostMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Ratio |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Capital Amount |  | 1,278,797 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_CullenFrostMember
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Ratio |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Minimum Capital Required for Capital Adequacy Purposes, Capital Amount |  | 1,072,035 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_CullenFrostMember
Leverage Ratio, Minimum Capital Required for Capital Adequacy Purposes, Ratio |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = cfr_CullenFrostMember
Frost Bank [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Common Equity Tier 1 to Risk-Weighted Assets, Actual, Capital Amount | 2,018,046 cfr_CommonEquityTierOneCapital / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Actual , Ratio | 11.95%cfr_ExcessCommonEquityTierOneCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 760,250 cfr_CommonEquityTierOneCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 4.50%cfr_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,182,155 cfr_CommonEquityTierOneCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased In, Ratio | 7.00%cfr_CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Capital Amount | 1,098,139 cfr_CommonEquityTierOneCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember |
Common Equity Tier 1 to Risk-Weighted Assets, Required To Be Considered Well Capitalized, Ratio | 6.50%cfr_CommonEquityTierOneCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember |
Tier 1 Capital to Risk-Weighted Assets, Actual, Capital Amount | 2,018,046 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = cfr_FrostBankMember | 1,979,415 us-gaap_TierOneRiskBasedCapital / dei_LegalEntityAxis = cfr_FrostBankMember
Tier 1 Capital to Risk-Weighted Assets, Actual, Ratio | 11.95%us-gaap_ExcessTierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 12.41%us-gaap_ExcessTierOneRiskBasedCapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,013,666 cfr_TierOneRiskBasedCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 6.00%cfr_TierOneRiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,435,474 cfr_TierOneRiskBasedCapitalRequiredForCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 8.50%cfr_TierOneRiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount | 1,351,555 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember | 956,894 us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Actual, Capital Amount | 2,123,754 us-gaap_Capital / dei_LegalEntityAxis = cfr_FrostBankMember | 2,071,012 us-gaap_Capital / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Actual, Ratio | 12.57%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 12.99%us-gaap_CapitalToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,351,555 cfr_CapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Phase - In Schedule, Ratio | 8.00%cfr_CapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,773,232 cfr_CapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Total Capital to Risk-Weighted Assets, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 10.50%cfr_CapitalRequiredforCapitalAdequacytoRiskWeightedAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Capital Amount | 1,689,444 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember | 1,594,823 us-gaap_CapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Actual, Capital Amount | 2,018,046 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = cfr_FrostBankMember | 1,979,415 us-gaap_TierOneLeverageCapital / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Actual, Ratio | 7.46%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 7.40%us-gaap_TierOneLeverageCapitalToAverageAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Minimum Capital Required - Basel III Phase-In Schedule, Capital Amount | 1,081,781 cfr_TierOneLeverageCapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Leverage Ratio, Minimum Capital Required - Basel III Phase-In Schedule, Ratio | 4.00%cfr_TierOneLeverageCapitalRequiredforCapitalAdequacytoAverageAssetsMinimumCapitalRequiredBaselIIIPhaseInSchedule / dei_LegalEntityAxis = cfr_FrostBankMember |
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Capital Amount | 1,081,520 cfr_TierOneLeverageCapitalRequiredforCapitalAdequacyMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Leverage Ratio, Minimum Capital Required - Basel III Fully Phased-In, Ratio | 4.00%cfr_TierOneLeverageCapitalRequiredforCapitalAdequacytoAverageAssetsMinimumCapitalRequiredBaselIIIFullyPhasedIn / dei_LegalEntityAxis = cfr_FrostBankMember |
Leverage Ratio, Required to be Considered Well Capitalized, Capital Amount | 1,352,226 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember | 1,337,636 us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Required to be Considered Well Capitalized, Ratio | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = cfr_FrostBankMember | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Capital Amount |  | 637,929 us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_FrostBankMember
Tier 1 Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Ratio |  | 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Capital Amount |  | 1,275,858 us-gaap_CapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_FrostBankMember
Total Capital to Risk-Weighted Assets, Minimum Required for Capital Adequacy Purposes, Ratio |  | 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Minimum Capital Required for Capital Adequacy Purposes, Capital Amount |  | $ 1,070,109 us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy / dei_LegalEntityAxis = cfr_FrostBankMember
Leverage Ratio, Minimum Capital Required for Capital Adequacy Purposes, Ratio |  | 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets / dei_LegalEntityAxis = cfr_FrostBankMember

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- Definition Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Minimum Capital Required Basel III Phase In Schedule + References No definition available. + Details
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- Definition The amount of total capital as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826 Reference 3: 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 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998 + Details
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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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- Definition The minimum Total risk based capital ratio (total capital divided by risk weighted assets) 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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Total Capital required to be categorized as well as capitalized 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 1 -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Total Capital divided by risk weighted assets as defined in the regulations. + 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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- Definition The amount of excess Tier 1 Risk Based Capital (which consists of the types of financial capital considered the most reliable and liquid, primarily Shareholders' equity. Examples of Tier 1 capital are common stock or unit, preferred stock or unit that is irredeemable and noncumulative, and retained earnings) divided by risk-weighted assets which are assets that are weighted for credit risk according to a formula used by the Reserve Bank. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital. + 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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- Definition The minimum amount of Tier 1 Leverage 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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- Definition The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations. + 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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in 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 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition Tier 1 Risk Based Capital as defined in the regulations. + 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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- Definition The minimum 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 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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826 + Details
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