cm:Concept: us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities
       
          
          | Proceeds from Sale of Securities, Operating Activities | 
       
       
          
          | us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities | 
       
       
          
          | Cash received from sale of investments in debt and equity securities, classified as operating activities, during the period; includes trading securities and any other investments classified as operating. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromSaleOfSecuritiesOperatingActivities |