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Revenue from Contracts with Customers (Narrative) (Details) | 9 Months Ended
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Sep. 30, 2022
Revenue from Contract with Customer [Abstract] |
Percent of Revenue not in scope of ASC 606 | 63.00%
Consumer segment |
Revenue, Major Customer [Line Items] |
Deposit fee revenue by segment | 41.00%
Commercial segment |
Revenue, Major Customer [Line Items] |
Deposit fee revenue by segment | 58.00%

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- Definition Portion of deposit fee revenue recorded in segment. + References No definition available. + Details
Name: | cbsh_DepositFeeRevenueBySegment
Namespace Prefix: | cbsh_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percent of total revenue not within the scope of ASC 606 + References No definition available. + Details
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Namespace Prefix: | cbsh_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- 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_EntityWideRevenueMajorCustomerLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cbsh_ConsumerSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cbsh_CommercialSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |