Deposits (Additional Information About Corporation's Deposits) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deposits [Abstract]
Deposits from the Certificate of Deposit Account Registry Service (CDARS)	$ 22	$ 200
Promontory Interfinancial Network Insured Cash Sweep Service	149	0
Deposits from foreign sources (primarily Mexico)	744,295us-gaap_DepositsForeign	769,970us-gaap_DepositsForeign
Deposits from certain directors, executive officers and their affiliates	$ 176,821us-gaap_RelatedPartyDepositLiabilities	$ 144,216us-gaap_RelatedPartyDepositLiabilities

This element represents Certificate Of Deposit Account Registry Service (CDARS) deposits held

No definition available.

Name:	cfr_CertificateOfDepositAccountRegistryServiceCdarsDepositsHeld
Namespace Prefix:	cfr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Promontory Interfinancial Network Insured Cash Sweep Service

+ References

No definition available.

+ Details

Name:	cfr_PromontoryInterfinancialNetworkInsuredCashSweepService
Namespace Prefix:	cfr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DepositsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate of all foreign interest-bearing and noninterest-bearing deposit liabilities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 235

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-05(a))

-URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537907-122884

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Subparagraph a

-Article 9

+ Details

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

- Definition

Amount of deposits held by the entity for a related party (entity, shareholder, employee).

+ 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.(k))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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