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Loans (Weighted Average Risk Grades for All Commercial Loans b Class) (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 Grade | Dec. 31, 2013 Grade
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans | $ 5,767,743 us-gaap_LoansReceivableCommercialAndIndustrial | $ 4,907,076 us-gaap_LoansReceivableCommercialAndIndustrial
Loans | 4,002,097 us-gaap_LoansReceivableCommercialRealEstate | 3,467,336 us-gaap_LoansReceivableCommercialRealEstate
Loans | 629,988 us-gaap_LoansReceivableCommercialConstruction | 426,639 us-gaap_LoansReceivableCommercialConstruction
Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 5.45 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember | 5.40 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember
Loans | 1,773,945 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember | 1,115,409 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember
Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 6.16 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember | 6.27 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember
Loans | 3,993,798 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember | 3,791,667 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember
Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 6.76 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember | 6.83 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember
Loans | 3,372,109 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember | 3,040,697 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember
Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 6.97 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember | 7.10 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
Loans | 629,988 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember | 426,639 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
Risk Grade One To Eight [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 5.37 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 5.37 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Loans | 1,740,455 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 1,106,348 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Risk Grade One To Eight [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 5.93 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 5.95 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Loans | 3,785,171 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 3,507,963 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Risk Grade One To Eight [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 6.53 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 6.59 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Loans | 3,148,339 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 2,844,665 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Risk Grade One To Eight [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 6.91 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 7.05 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Loans | 617,805 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 418,999 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember
Risk Grade Nine [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Loans | 27,313 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 7,726 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Risk Grade Nine [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Loans | 65,166 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 74,766 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Risk Grade Nine [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Loans | 72,906 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 65,770 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Risk Grade Nine [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Loans | 8,003 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 1,301 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember
Risk Grade Ten [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Loans | 161 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 245 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Risk Grade Ten [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Loans | 54,519 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 89,878 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Risk Grade Ten [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Loans | 87,889 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 49,881 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Risk Grade Ten [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Loans | 1,323 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 5,931 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember
Risk Grade Eleven [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Loans | 5,380 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 500 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Risk Grade Eleven [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Loans | 55,034 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 92,917 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Risk Grade Eleven [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Loans | 43,336 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 53,208 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Risk Grade Eleven [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Loans | 64 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 408 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember
Risk Grade Twelve [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Loans | 636 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 590 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Risk Grade Twelve [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Loans | 31,683 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 21,389 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Risk Grade Twelve [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Loans | 19,501 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 24,387 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Risk Grade Twelve [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Loans | 2,793 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 0 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember
Risk Grade Thirteen [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Loans | 0 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 0 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Risk Grade Thirteen [Member] | Commercial and Industrial, Other Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Loans | 2,225 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 4,754 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Risk Grade Thirteen [Member] | Commercial Real Estate, Buildings, Land and Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Loans | 138 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 2,786 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Risk Grade Thirteen [Member] | Commercial Real Estate, Construction [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Loans | $ 0 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | $ 0 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember
Minimum [Member] | Risk Grade One To Eight [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 1.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember / us-gaap_RangeAxis = us-gaap_MinimumMember | 1.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember / us-gaap_RangeAxis = us-gaap_MinimumMember
Maximum [Member] | Risk Grade One To Eight [Member] | Commercial and Industrial, Energy [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Weighted Average Risk Grade | 8.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember / us-gaap_RangeAxis = us-gaap_MaximumMember | 8.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember / us-gaap_RangeAxis = us-gaap_MaximumMember

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