cm:Level3TextBlock: us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTableTextBlock
       
          
          | Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table Text Block] | 
       
       
          
          | us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTableTextBlock | 
       
       
          
          | Tabular disclosure of the nature and risks of short-term collateralized financing obtained through repurchase agreements, securities lending transactions and repurchase-to-maturity transactions, accounted for as secured borrowings. | 
       
       
          
          | cm:Level3TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:TransferOfCertainFinancialAssetsAccountedForAsSecuredBorrowingsTableTextBlock |