cm:Level1TextBlock: us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock
       
          
          | Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] | 
       
       
          
          | us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock | 
       
       
          
          | The entire disclosure for repurchase agreements (also known as repos), resale agreements (also known as reverse repurchase agreements or reverse repos), securities borrowed transactions, and securities loaned transactions. | 
       
       
          
          | cm:Level1TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock |