cm:Concept: us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
       
          
          | Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability | 
       
       
          
          | us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1 | 
       
       
          
          | Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1 |