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Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Commitments And Guarantees [Line Items] |  |  |
Credit card guarantees | $ 8,900,000 cfr_CreditCardGuarantees | $ 8,400,000 cfr_CreditCardGuarantees |
Fully collateralized credit card guarantees | 1,500,000 cfr_CollateralizedCreditCardGuarantees | 1,200,000 cfr_CollateralizedCreditCardGuarantees |
Minimum percentage of collateral required for securities borrowed | 100.00%cfr_MinimumPercentageOfCollateralRequiredForSecuritiesBorrowed |  |
Maximum future payments guaranteed | 2,500,000,000 cfr_MaximumFuturePaymentsGuaranteed |  |
Held in trust liquid assets as collateral | 2,500,000,000 us-gaap_AssetsHeldInTrust |  |
Rent expense for operating leases | 28,200,000 us-gaap_OperatingLeasesRentExpenseNet | 24,600,000 us-gaap_OperatingLeasesRentExpenseNet | 22,700,000 us-gaap_OperatingLeasesRentExpenseNet
Aggregate future minimum rentals to be received under non-cancelable subleases greater than one year | 209,000 us-gaap_OperatingLeasesFutureMinimumPaymentsReceivable |  |
Partnership Interest of a Director [Member] |  |  |
Commitments And Guarantees [Line Items] |  |  |
Rent expense for operating leases | $ 925,000 us-gaap_OperatingLeasesRentExpenseNet / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = us-gaap_PartnershipInterestMember | $ 871,000 us-gaap_OperatingLeasesRentExpenseNet / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = us-gaap_PartnershipInterestMember | $ 902,000 us-gaap_OperatingLeasesRentExpenseNet / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = us-gaap_PartnershipInterestMember

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- Definition Collateralized Credit Card Guarantees + References No definition available. + Details
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Balance Type: | debit
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- Details
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- Definition Credit Card Guarantees + References No definition available. + Details
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- Definition Maximum Future Payments Guaranteed + References No definition available. + Details
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- Definition Minimum Percentage Of Collateral Required For Securities Borrowed + References No definition available. + Details
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- Definition The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(b)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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- Definition Future minimum rental payments in aggregate as of the balance sheet date under operating leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718 + Details
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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
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- Details
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