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Derivative Financial Instruments - Additional Information (Detail) (USD $) | 3 Months Ended | 1 Months Ended
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Oct. 31, 2007
Derivative [Line Items] |  |  |
Deferred accumulated gain |  | $ 21,300,000 us-gaap_DerivativeInstrumentsGainRecognizedInOtherComprehensiveIncomeEffectivePortion |
Deferred accumulated after-tax gain |  | 13,800,000 us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet |
Weighted-average strike rate for outstanding interest rate caps | 2.98%cfr_WeightedAverageStrikeRateOutstandingInterestRateCaps |  |
Approximate credit exposure related to swaps with bank customers | 47,000,000 us-gaap_CreditDerivativeMaximumExposureUndiscounted |  |
Aggregate fair value of securities posted as collateral for derivative contracts | 23,600,000 us-gaap_PledgedAssetsSeparatelyReportedSecuritiesPledgedAsCollateralAtFairValue |  |
Cash collateral for borrowed securities | 19,400,000 us-gaap_CashCollateralForBorrowedSecurities |  |
Interest Rate Swaps With Upstream Financial Institution Counterparties [Member] |  |  |
Derivative [Line Items] |  |  |
Approximate credit exposure related to swaps with bank customers | 9,200,000 us-gaap_CreditDerivativeMaximumExposureUndiscounted / us-gaap_DerivativeByNatureAxis = cfr_InterestRateSwapsWithUpstreamFinancialInstitutionCounterpartiesMember |  |
Variable-Rate Loans Outstanding [Member] |  |  |
Derivative [Line Items] |  |  |
Notional amount of interest rate swap contracts |  |  | 1,200,000,000 invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember
Principal amount outstanding of variable-rate loans |  |  | $ 1,200,000,000 us-gaap_PrincipalAmountOutstandingOfLoansHeldInPortfolio / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember
Period for which cash flow hedges were used to hedge monthly interest receipts |  |  | 84 months

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- Definition Period For Which Cash Flow Hedges Were Used To Hedge Monthly Interest Receipts + References No definition available. + Details
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- Definition Weighted Average Strike Rate Outstanding Interest Rate Caps + References No definition available. + Details
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.1) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.(a),2) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Credit Derivative -URI http://asc.fasb.org/extlink&oid=6854095 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4K -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5708775-113959 + Details
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- Definition The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 + Details
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- Definition The effective portion of gains on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959 + Details
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- Details
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- Definition The sum of the fair values, as of the date of each statement of financial position presented, of securities that are restricted as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728 + Details
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- Definition This is the result of the principal amount outstanding of total loans managed or securitized less securitized loans and loans that are in the process of being securitized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51814546&loc=d3e107314-111719 + Details
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- Details
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