cm:Concept: us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsNumberOfSharesIndexed
       
          
          | Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Number of Shares Indexed | 
       
          
          | us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsNumberOfSharesIndexed | 
       
          
          | For a forward contract or an option indexed to the issuer's equity shares, the number of issuer's shares to which the contract is indexed. | 
       
          
          | cm:Concept | 
       
          
          | Shares (xbrli:sharesItemType) | 
       
          
          | As Of (instant) | 
       
          
          | (no balance type) | 
       
          
          | false | 
       
          
          | us-gaap:SharesSubjectToMandatoryRedemptionSettlementTermsNumberOfSharesIndexed |