cm:Concept: us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral
       
          
          | Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral | 
       
       
          
          | us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral | 
       
       
          
          | Amount, after effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price offset against a right to receive collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:SecuritiesSoldUnderAgreementsToRepurchaseAmountOffsetAgainstCollateral |