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Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | $ 29,921 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral | $ 16,265 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (20,436)us-gaap_DerivativeCollateralObligationToReturnSecurities | (14,824)us-gaap_DerivativeCollateralObligationToReturnSecurities
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | (6,035)us-gaap_DerivativeCollateralObligationToReturnCash | (1,360)us-gaap_DerivativeCollateralObligationToReturnCash
Net Amount, Derivatives, Financial Assets | 3,450 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral | 81 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
Net Amount Recognized, Resell Agreements, Financial Assets | 9,642 us-gaap_SecuritiesBorrowedNotSubjectToMasterNettingArrangement | 7,898 us-gaap_SecuritiesBorrowedNotSubjectToMasterNettingArrangement
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets | 0 us-gaap_SecuritiesPurchasedUnderAgreementsToResellCollateralObligationToReturnSecurities | 0 us-gaap_SecuritiesPurchasedUnderAgreementsToResellCollateralObligationToReturnSecurities
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets | (9,642)us-gaap_DerivativeAssetSecuritiesPurchasedUnderAgreementsToResellSecuritiesBorrowedCollateralObligationToReturnCash | (7,898)us-gaap_DerivativeAssetSecuritiesPurchasedUnderAgreementsToResellSecuritiesBorrowedCollateralObligationToReturnCash
Net Amount, Resell Agreements, Financial Assets | 0 us-gaap_SecuritiesBorrowedAmountOffsetAgainstCollateral | 0 us-gaap_SecuritiesBorrowedAmountOffsetAgainstCollateral
Net Amount Recognized, Total Financial Assets | 39,563 cfr_FinancialAssetsDerivativesAndRepurchaseAgreementsNet | 24,163 cfr_FinancialAssetsDerivativesAndRepurchaseAgreementsNet
Gross Amounts Not Offset, Collateral, Financial Assets | (15,677)cfr_FinancialAssetsDerivativeAndResellAgreementsCollateralAmountNotOffset | (9,258)cfr_FinancialAssetsDerivativeAndResellAgreementsCollateralAmountNotOffset
Net Amount, Financial Assets | 3,450 cfr_FinancialAssetsDerivativeAssetsAndResellAgreementsNetOfAmountNotOffset | 81 cfr_FinancialAssetsDerivativeAssetsAndResellAgreementsNetOfAmountNotOffset
Net Amount Recognized, Derivatives, Financial Liabilities | 47,898 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral | 42,603 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (20,436)us-gaap_DerivativeCollateralRightToReclaimSecurities | (14,824)us-gaap_DerivativeCollateralRightToReclaimSecurities
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (26,307)us-gaap_DerivativeCollateralRightToReclaimCash | (27,012)us-gaap_DerivativeCollateralRightToReclaimCash
Net Amount, Derivatives, Financial Liabilities | 1,155 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral | 767 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
Net Amount Recognized, Repurchase Agreements, Financial Liabilities | 791,119 us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseNotSubjectToMasterNettingArrangement | 668,053 us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseNotSubjectToMasterNettingArrangement
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities | 0 us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimSecurities | 0 us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimSecurities
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities | (791,119)us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimCash | (668,053)us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimCash
Net Amount, Repurchase Agreements, Financial Liabilities | 0 us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedAmountOffsetAgainstCollateral | 0 us-gaap_DerivativeLiabilitySecuritiesSoldUnderAgreementsToResellSecuritiesLoanedAmountOffsetAgainstCollateral
Net Amount Recognized, Financial Liabilities | 839,017 cfr_FinancialLiabilitiesDerivativesAndRepurchaseAgreementsNet | 710,656 cfr_FinancialLiabilitiesDerivativesAndRepurchaseAgreementsNet
Gross Amounts Not Offset, Collateral, Financial Liabilities | (817,426)cfr_FinancialLiabilitiesDerivativeAndRepurchaseAgreementsCollateralAmountNotOffset | (695,065)cfr_FinancialLiabilitiesDerivativeAndRepurchaseAgreementsCollateralAmountNotOffset
Net Amount, Financial Liabilities | 1,155 cfr_FinancialInstrumentsDerivativeLiabilitiesAndRepurchaseAgreementsNetOfAmountNotOffset | 767 cfr_FinancialInstrumentsDerivativeLiabilitiesAndRepurchaseAgreementsNetOfAmountNotOffset
Counterparty A [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 627 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | 3,342 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (627)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | (3,342)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | 0 us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Net Amount, Derivatives, Financial Assets | 0 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | 0 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Net Amount Recognized, Derivatives, Financial Liabilities | 18,653 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | 18,615 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (627)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | (3,342)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (17,626)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | (15,167)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Net Amount, Derivatives, Financial Liabilities | 400 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember | 106 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartyaMember
Counterparty B [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 17,308 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | 8,196 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (9,506)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | (8,196)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | (4,925)us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | 0 us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Net Amount, Derivatives, Financial Assets | 2,877 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | 0 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Net Amount Recognized, Derivatives, Financial Liabilities | 9,506 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | 9,054 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (9,506)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | (8,196)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | 0 us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | (613)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Net Amount, Derivatives, Financial Liabilities | 0 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember | 245 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartybMember
Counterparty C [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 7,991 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | 1,187 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (7,539)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | (1,187)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | 0 us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Net Amount, Derivatives, Financial Assets | 452 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | 0 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Net Amount Recognized, Derivatives, Financial Liabilities | 7,539 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | 10,870 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (7,539)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | (1,187)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | 0 us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | (9,683)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Net Amount, Derivatives, Financial Liabilities | 0 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember | 0 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_CounterpartycMember
Other Counterparties [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 3,995 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | 3,540 us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (2,764)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | (2,099)us-gaap_DerivativeCollateralObligationToReturnSecurities / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | (1,110)us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | (1,360)us-gaap_DerivativeCollateralObligationToReturnCash / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Net Amount, Derivatives, Financial Assets | 121 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | 81 us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Net Amount Recognized, Derivatives, Financial Liabilities | 12,200 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | 4,064 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (2,764)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | (2,099)us-gaap_DerivativeCollateralRightToReclaimSecurities / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (8,681)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | (1,549)us-gaap_DerivativeCollateralRightToReclaimCash / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember
Net Amount, Derivatives, Financial Liabilities | $ 755 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember | $ 416 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral / us-gaap_CounterpartyNameAxis = cfr_OtherCounterpartiesMember

X
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- Definition Financial Assets Derivative Assets And Resell Agreements Net Of Amount Not Offset + References No definition available. + Details
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- Definition Financial Instruments Derivative Liabilities And Repurchase Agreements Net Of Amount Not Offset + References No definition available. + Details
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- Definition Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets, securities purchased under agreements to resell and securities borrowed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226016-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312 + Details
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- Definition Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226016-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41678-113959 + Details
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