Balance Sheet Offsetting - Financial Instruments Eligible for Offset Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	$ 28,161	$ 29,921
Gross Amount Offset, Derivatives, Financial assets	0cfr_DerivativeAssetsGrossOffset	0cfr_DerivativeAssetsGrossOffset
Net Amount Recognized, Derivatives, Financial assets	28,161us-gaap_DerivativeAssets	29,921us-gaap_DerivativeAssets
Gross Amount Recognized, Resell agreements, Financial assets	9,642	9,642
Gross Amount Offset, Resell agreements, Financial assets	0cfr_ResellAgreementGrossOffset	0cfr_ResellAgreementGrossOffset
Net Amount Recognized, Resell agreements, Financial assets	9,642	9,642
Gross Amount Recognized, Financial assets	37,803cfr_FinancialAssetsGross	39,563cfr_FinancialAssetsGross
Gross Amount Offset, Financial assets	0cfr_FinancialAssetsGrossOffset	0cfr_FinancialAssetsGrossOffset
Net Amount Recognized, Financial assets	37,803	39,563
Gross Amount Recognized, Derivatives, Financial Liabilities	55,894	47,898
Gross Amount Offset, Derivatives, Financial liabilities	0cfr_DerivativeLiabilitiesGrossOffset	0cfr_DerivativeLiabilitiesGrossOffset
Net Amount Recognized, Derivatives, Financial liabilities	55,894us-gaap_DerivativeLiabilities	47,898us-gaap_DerivativeLiabilities
Gross Amount Recognized, Repurchase agreements, Financial liabilities	593,107	791,119
Gross Amount Offset, Repurchase agreements, Financial liabilities	0	0
Net Amount Recognized, Repurchase agreements, Financial liabilities	593,107	791,119
Gross Amount Recognized, Financial liabilities	649,001	839,017
Gross Amount Offset, Financial liabilities	0	0
Net Amount Recognized, Financial Liabilities	649,001	839,017
Loan/lease interest rate swaps and caps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	1,193	2,191
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	1,193	2,191
Commodity swaps and options [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	26,626	27,064
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	26,626	27,064
Gross Amount Recognized, Derivatives, Financial Liabilities	5,712	5,765
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	5,712	5,765
Foreign currency forward contracts [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Assets	342	666
Gross Amount Offset, Derivatives, Financial assets	0	0
Net Amount Recognized, Derivatives, Financial assets	342	666
Gross Amount Recognized, Derivatives, Financial Liabilities		2
Gross Amount Offset, Derivatives, Financial liabilities		0
Net Amount Recognized, Derivatives, Financial liabilities		2
Loan/lease interest rate swaps [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Gross Amount Recognized, Derivatives, Financial Liabilities	50,182	42,131
Gross Amount Offset, Derivatives, Financial liabilities	0	0
Net Amount Recognized, Derivatives, Financial liabilities	$ 50,182	$ 42,131

Derivative Assets Gross Offset

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Derivative Liabilities Gross Offset

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Financial Assets Derivatives And Resell Agreements Net

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Financial Assets Gross

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Financial Assets Gross Offset

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Financial Instruments Liabilities Gross

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Financial Liabilities Derivatives And Repurchase Agreements Net

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Repurchase Agreements Liabilities Gross Offset

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Resell Agreement Gross Offset

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- Definition

Amount to be repaid to the counterparty to the repurchase agreement when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under the repurchase agreement exceeds 10 percent of total assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

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-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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This is the total amount of resale agreements as of the reporting date. This is a gross amount (does not net agreement amounts by counterparty).

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Amount, before effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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