XML 171 R155.htm IDEA: XBRL DOCUMENT
v3.20.4

Commitments, Contingencies And Guarantees (Schedule Of Off-Balance Sheet Instruments Commitments) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Commercial letters of credit | $ 3,117 | $ 7,050
Credit Card [Member] |  |
Commitments to extend credit | 4,972,104 | 5,063,166
Other [Member] |  |
Commitments to extend credit | 8,033,222 | 6,123,264
Financial Standby Letter of Credit [Member] |  |
Standby letters of credit, net of participations | $ 357,087 | $ 377,338

X
- Definition Commercial letters of credit. + References No definition available. + Details
Name: | cbsh_CommercialLettersOfCredit
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Commitment To Extend Credit + References No definition available. + Details
Name: | cbsh_CommitmentToExtendCredit
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CreditCardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherCreditDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_FinancialStandbyLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |