cm:Concept: us-gaap:SecuritiesLoanedNotSubjectToMasterNettingArrangementDeduction
       
          
          | Securities Loaned, Not Subject to Master Netting Arrangement Deduction | 
       
       
          
          | us-gaap:SecuritiesLoanedNotSubjectToMasterNettingArrangementDeduction | 
       
       
          
          | Amount of securities loaned to entities in exchange for collateral, not subject to a master netting arrangement, deducted from securities loaned. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesLoanedNotSubjectToMasterNettingArrangementDeduction |