cm:Concept: us-gaap:SecuritiesBorrowedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection
       
          
          | Securities Borrowed, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election | 
       
       
          
          | us-gaap:SecuritiesBorrowedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection | 
       
       
          
          | Amount, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of securities borrowed from entities in exchange for collateral, offset against an obligation to return collateral under a master netting arrangement. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesBorrowedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection |