cm:Concept: us-gaap:ObligationToReturnSecuritiesReceivedAsCollateral
       
          
          | Obligation to Return Securities Received as Collateral | 
       
          
          | us-gaap:ObligationToReturnSecuritiesReceivedAsCollateral | 
       
          
          | The fair value of collateral received by the entity associated with securities borrowed that must be returned if the counterparty fulfills its obligations. It appears on the balance sheet as a liability and has a corresponding asset that appears on the balance sheet called Securities Received as Collateral. | 
       
          
          | cm:Concept | 
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
          
          | As Of (instant) | 
       
          
          | Credit | 
       
          
          | false | 
       
          
          | us-gaap:ObligationToReturnSecuritiesReceivedAsCollateral |