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Summary of Significant Accounting Policies (Narrative) (Detail) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Cash on hand or on deposit required | 175,600,000 us-gaap_CashReserveDepositRequiredAndMade | $ 116,600,000 us-gaap_CashReserveDepositRequiredAndMade
Cash collateral on deposit | 12,100,000 us-gaap_CashCollateralForBorrowedSecurities |
Foreclosed assets | 5,300,000 us-gaap_ForeclosedAssets | $ 11,900,000 us-gaap_ForeclosedAssets
Minimum [Member] |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Range of change in fair value of derivative hedging instrument to be considered highly effective | 80.00%cfr_RangeOfChangeInFairValueOfDerivativeHedgingInstrumentToBeConsideredHighlyEffective / us-gaap_RangeAxis = us-gaap_MinimumMember |
Maximum [Member] |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Range of change in fair value of derivative hedging instrument to be considered highly effective | 125.00%cfr_RangeOfChangeInFairValueOfDerivativeHedgingInstrumentToBeConsideredHighlyEffective / us-gaap_RangeAxis = us-gaap_MaximumMember |

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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 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 7 + Details
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- Definition Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 305 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792 + Details
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