cm:Level3TextBlock: us-gaap:ScheduleOfOtherInvestmentsNotReadilyMarketableTextBlock
       
          
          | Other Investments Not Readily Marketable [Table Text Block] | 
       
       
          
          | us-gaap:ScheduleOfOtherInvestmentsNotReadilyMarketableTextBlock | 
       
       
          
          | Tabular disclosure of other investments not readily marketable, including, but not limited to, description of investment, fair value and value as measured by quoted price. | 
       
       
          
          | cm:Level3TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ScheduleOfOtherInvestmentsNotReadilyMarketableTextBlock |