cm:Concept: us-gaap:SecuritiesReceivedAsCollateralAmountRepledgedAndSold
       
          
          | Securities Received as Collateral, Amount Repledged and Sold | 
       
       
          
          | us-gaap:SecuritiesReceivedAsCollateralAmountRepledgedAndSold | 
       
       
          
          | The fair value of collateral received that has been sold or re-pledged and is owed to the debtor (transferor) upon settlement of the related contractual obligation under which it was received. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesReceivedAsCollateralAmountRepledgedAndSold |