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Off-Balance-Sheet Arrangements, Commitments, Guarantees and Contingencies (Financial Instruments With Off-Balance-Sheet Risk) (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Standby Letters of Credit [Member]    
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Financial instruments with off- balance-sheet risk $ 248,360us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_StandbyLettersOfCreditMember		 $ 186,857us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_StandbyLettersOfCreditMember
Commitments to Extend Credit [Member]    
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Financial instruments with off- balance-sheet risk 7,955,779us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommitmentsToExtendCreditMember		 6,919,942us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommitmentsToExtendCreditMember
Deferred Standby Letter of Credit Fees [Member]    
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Financial instruments with off- balance-sheet risk $ 1,942us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_FinancialInstrumentAxis
= cfr_DeferredStandbyLetterOfCreditFeesMember		 $ 1,450us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
/ us-gaap_FinancialInstrumentAxis
= cfr_DeferredStandbyLetterOfCreditFeesMember