cm:Concept: us-gaap:SecuritiesPurchasedUnderAgreementsToResellAmountOffsetAgainstCollateral
       
          
          | Securities Purchased under Agreements to Resell, Amount Offset Against Collateral | 
       
       
          
          | us-gaap:SecuritiesPurchasedUnderAgreementsToResellAmountOffsetAgainstCollateral | 
       
       
          
          | Amount, after effects of master netting arrangements, of funds outstanding loaned in the form of a security resale agreement between the entity and another party for the purchase and resale of identical or substantially the same securities at a date certain for a specified price offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesPurchasedUnderAgreementsToResellAmountOffsetAgainstCollateral |