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Fair Value Measurements - Additional Information (Detail) | 3 Months Ended
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Mar. 31, 2015 Grade
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
Weighted-average risk grade of loans underlying interest rate swaps measured at fair value | 11.0 cfr_WeightedAverageRiskGradeOfLoansUnderlyingInterestRateSwapsMeasuredAtFairValue
Default on the interest rate swaps, weighted average loss severity percentage | 20.00%us-gaap_FairValueInputsLossSeverity

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- Definition Weighted-Average Risk Grade Of Loans Underlying Interest Rate Swaps Measured At Fair Value. + References No definition available. + Details
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Namespace Prefix: | cfr_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration