XML 165 R149.htm IDEA: XBRL DOCUMENT
v3.20.4

Derivative Instruments (Summary Of The Effects Of Derivative Instruments On Consolidated Statements Of Income) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | $ 1,963 | $ 3,852 | $ 4,480
Other Non-Interest Income [Member] | Interest Rate Swaps [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | 317 | 4,732 | 3,914
Other Non-Interest Income [Member] | Interest Rate Caps [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | 20 | 0 | 11
Other Non-Interest Income [Member] | Credit Risk Participation Agreements [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | 413 | (16) | 150
Other Non-Interest Income [Member] | Foreign Exchange Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | (111) | 53 | 31
Loans Fees And Sales [Member] | Mortgage Loan Commitments [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | 2,768 | (77) | (45)
Loans Fees And Sales [Member] | Mortgage Loan Forward Sale Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | (4) | (3) | 5
Loans Fees And Sales [Member] | Forward Contracts [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | $ (1,440) | $ (837) | $ 414

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
Name: | us-gaap_GainLossOnDerivativeInstrumentsNetPretax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=cbsh_OtherNonInterestIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cbsh_CreditRiskParticipationAgreementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=cbsh_LoansFeesAndSalesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cbsh_MortgageLoanCommitmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cbsh_MortgageLoanForwardSaleContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |