cm:Concept: us-gaap:NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsNonredeemable
       
          
          | Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable | 
       
       
          
          | us-gaap:NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsNonredeemable | 
       
       
          
          | Amount after tax of income (loss) attributable to other nonredeemable noncontrolling equity holder. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsNonredeemable |