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v3.22.2.2

Resale and Repurchase Agreements (Narrative) (Details) - USD ($) $ in Millions | Sep. 30, 2022 | Dec. 31, 2021
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Collateral Swap [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Collateral Swap Agreements | $ 200.0 | $ 400.0

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- Definition [Line Items] for Balance Sheet Offsetting [Table] + References No definition available. + Details
Name: | cbsh_BalanceSheetOffsettingLineItems
Namespace Prefix: | cbsh_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Collateral Swap Agreements + References No definition available. + Details
Name: | cbsh_CollateralSwapAgreements
Namespace Prefix: | cbsh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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