Derivative Counter Party [Line Items]

No definition available.

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- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeAssetNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeLiabilityNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

+ Details

Name:	us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

+ References

+ Details

Name:	us-gaap_ForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	srt_CounterpartyNameAxis=cfr_FinancialInstitutionCounterpartiesMember
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- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherLiabilitiesMember
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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_CounterpartyNameAxis=cfr_CustomerCounterpartiesMember
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- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
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Data Type:	na
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cfr_GBPForeignExchangeForwardMember
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Data Type:	na
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cfr_MXNForeignExchangeForwardsMember
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Derivative Financial Instruments - Notional Amount and Fair Value of Foreign Currency Forward Contract (Detail) £ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands	Jun. 30, 2019 USD ($)	Jun. 30, 2019 CAD ($)	Jun. 30, 2019 MXN ($)	Jun. 30, 2019 GBP (£)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 CAD ($)	Dec. 31, 2018 MXN ($)	Dec. 31, 2018 GBP (£)
Financial Institution Counterparties [Member] \| Other Liabilities [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Liability Notional Amount		$ 5,339	$ 0	£ 0		$ 11,003	$ 3,015	£ 142
Customer Counterparties [Member] \| Other Assets [Member] \| Non Designated as Hedging Instrument [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Assets Notional Amount		$ 5,326	$ 0	£ 0		$ 10,979	$ 3,000	£ 145
Foreign Exchange Forward [Member] \| Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Liability Estimated Fair Value	$ (14)				$ (13)
Foreign Exchange Forward [Member] \| Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Assets Estimated Fair Value	27				40
GBP Foreign Exchange Forward [Member] \| Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Liability Estimated Fair Value	0				(2)
GBP Foreign Exchange Forward [Member] \| Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Assets Estimated Fair Value	0				4
MXN Foreign Exchange Forwards [Member] \| Financial Institution Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Liability Estimated Fair Value	0				(132)
MXN Foreign Exchange Forwards [Member] \| Customer Counterparties [Member]
Derivative Counter Party [Line Items]
Forward Contracts – Assets Estimated Fair Value	$ 0				$ 149