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Loans - Weighted Average Risk Grades for All Commercial Loans by Class (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2015 Grade | Dec. 31, 2014 Grade | Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans | $ 5,908,535 us-gaap_LoansReceivableCommercialAndIndustrial | $ 5,767,743 us-gaap_LoansReceivableCommercialAndIndustrial | $ 5,106,726 us-gaap_LoansReceivableCommercialAndIndustrial
Loans | 4,074,425 us-gaap_LoansReceivableCommercialRealEstate | 4,002,097 us-gaap_LoansReceivableCommercialRealEstate | 3,496,139 us-gaap_LoansReceivableCommercialRealEstate
Loans | 685,629 us-gaap_LoansReceivableCommercialConstruction | 629,988 us-gaap_LoansReceivableCommercialConstruction |
Commercial and industrial, Energy [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 6.07 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember | 5.45 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember |
Loans | 1,819,049 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember | 1,773,945 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 | 6.22 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember | 6.16 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember |
Loans | 4,089,486 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember | 3,993,798 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 | 6.82 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember | 6.76 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember |
Loans | 3,388,796 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember | 3,372,109 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember |
Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 7.13 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember | 6.97 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember |
Loans | 685,629 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember | 629,988 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember |
Risk grades 1-8 [Member] | Commercial and industrial, Energy [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 5.88 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 | 1,734,701 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 1,740,455 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Risk grades 1-8 [Member] | Commercial and industrial, Other commercial [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 5.97 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 5.93 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Loans | 3,848,801 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 3,785,171 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Risk grades 1-8 [Member] | Commercial real estate, Buildings, land and other [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 6.57 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 6.53 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Loans | 3,135,623 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 3,148,339 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Risk grades 1-8 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 6.98 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 6.91 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Loans | 639,505 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember | 617,805 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeOneToEightMember |
Risk grade 9 [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 | 24,922 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 27,313 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember |
Risk grade 9 [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 | 73,842 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 65,166 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember |
Risk grade 9 [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 | 104,344 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 72,906 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember |
Risk grade 9 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 9.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember |
Loans | 41,422 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember | 8,003 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeNineMember |
Risk grade 10 [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 | 36,632 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 161 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember |
Risk grade 10 [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 | 87,050 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 54,519 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember |
Risk grade 10 [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 | 90,872 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 87,889 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember |
Risk grade 10 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 10.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember |
Loans | 1,900 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember | 1,323 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTenMember |
Risk grade 11 [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 | 22,158 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 5,380 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember |
Risk grade 11 [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 | 46,828 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 55,034 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember |
Risk grade 11 [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 | 40,812 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 43,336 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember |
Risk grade 11 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 11.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember |
Loans | 62 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember | 64 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeElevenMember |
Risk grade 12 [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 | 636 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialEnergyFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember |
Risk grade 12 [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 | 30,980 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 31,683 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember |
Risk grade 12 [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 | 17,074 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 19,501 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember |
Risk grade 12 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 12.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember |
Loans | 2,740 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember | 2,793 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeTwelveMember |
Risk grade 13 [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 13 [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 | 1,985 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 2,225 us-gaap_LoansReceivableCommercialAndIndustrial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialAndIndustrialOtherCommercialFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember |
Risk grade 13 [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 | 71 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 138 us-gaap_LoansReceivableCommercialRealEstate / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = cfr_CommercialRealEstateBuildingsLandAndOtherFinancingReceivableMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember |
Risk grade 13 [Member] | Construction Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Weighted Average Risk Grade | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | 13.00 cfr_WeightedAverageRiskGradeForLoans / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember |
Loans | $ 0 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember | $ 0 us-gaap_LoansReceivableCommercialConstruction / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConstructionLoansMember / us-gaap_InternalCreditAssessmentAxis = cfr_RiskGradeThirteenMember |

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