XML 114 R97.htm IDEA: XBRL DOCUMENT
v3.20.4

Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Commitments And Guarantees [Line Items] |  |
Credit card guarantees | $ 9.1 | $ 8.5
Fully collateralized credit card guarantees | $ 8.2 | $ 1.3

X
- Definition Collateralized Credit Card Guarantees + References No definition available. + Details
Name: | cfr_CollateralizedCreditCardGuarantees
Namespace Prefix: | cfr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Commitments And Guarantees [Line Items] + References No definition available. + Details
Name: | cfr_CommitmentsAndGuaranteesLineItems
Namespace Prefix: | cfr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Credit Card Guarantees + References No definition available. + Details
Name: | cfr_CreditCardGuarantees
Namespace Prefix: | cfr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration