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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	175,600,000us-gaap_CashReserveDepositRequiredAndMade	$ 116,600,000us-gaap_CashReserveDepositRequiredAndMade
Cash collateral on deposit	12,100,000us-gaap_CashCollateralForBorrowedSecurities
Foreclosed assets	5,300,000us-gaap_ForeclosedAssets	$ 11,900,000us-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

Range Of Change In Fair Value Of Derivative Hedging Instrument To Be Considered Highly Effective

+ References

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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

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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

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Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4437-111522

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