cm:Concept: us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments
       
          
          | Proceeds from Maturities, Prepayments and Calls of Other Investments | 
       
       
          
          | us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments | 
       
       
          
          | The cash inflow associated with the maturity (principal being due), prepayment and call (request of early payment) of other investments not otherwise defined in the taxonomy. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfOtherInvestments |