cm:Concept: us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValueFairValueElection
       
          
          | Equity Securities without Readily Determinable Fair Value, Fair Value Election [true false] | 
       
       
          
          | us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValueFairValueElection | 
       
       
          
          | Indicates (true false) whether measurement method changed to fair value for equity security without readily determinable fair value. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Yes/No (xbrli:booleanItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValueFairValueElection |