cm:Concept: us-gaap:ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset
       
          
          | Consideration Received for Beneficial Interest Obtained for Transferring Financial Asset | 
       
       
          
          | us-gaap:ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset | 
       
       
          
          | Amount of beneficial interest received as consideration for transferring noncash financial asset. Includes, but is not limited to, trade receivable in securitization transaction. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset |