cm:Concept: us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment
       
          
          | Proceeds from Principal Repayments on Loans and Leases Held-for-investment | 
       
       
          
          | us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment | 
       
       
          
          | The cash inflow from repayments of the balance excluding interest (principal) on loans receivable and leases held for investment purposes. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromPrincipalRepaymentsOnLoansAndLeasesHeldForInvestment |