cm:Concept: us-gaap:LoansAndLeasesReceivableCollateralForSecuredBorrowings
       
          
          | Loans and Leases Receivable, Collateral for Secured Borrowings | 
       
          
          | us-gaap:LoansAndLeasesReceivableCollateralForSecuredBorrowings | 
       
          
          | Reflects the aggregate value of loans, trade receivables, securities and financial instruments that serve as collateral for obligations arising from a transfer of financial assets recorded as a secured borrowing. | 
       
          
          | cm:Concept | 
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
          
          | As Of (instant) | 
       
          
          | Debit | 
       
          
          | false | 
       
          
          | us-gaap:LoansAndLeasesReceivableCollateralForSecuredBorrowings |