cm:Concept: us-gaap:SecuritiesLoanedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection
       
          
          | Securities Loaned, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election | 
       
       
          
          | us-gaap:SecuritiesLoanedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection | 
       
       
          
          | Amount, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, of securities loaned to entities in exchange for collateral, offset against a right to receive collateral. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesLoanedOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection |