cm:Concept: us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfSecuritiesOperatingActivities
       
          
          | Proceeds from Maturities, Prepayments and Calls of Securities, Operating Activities | 
       
       
          
          | us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfSecuritiesOperatingActivities | 
       
       
          
          | Cash received from maturities, prepayments and calls of trading securities and other securities, classified as operating. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfSecuritiesOperatingActivities |