cm:Concept: us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged
       
          
          | Customer Securities for which Entity has Right to Sell or Repledge, Fair Value of Securities Sold or Repledged | 
       
       
          
          | us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged | 
       
       
          
          | Fair value as of the balance sheet date of customer securities accepted as collateral by the entity that it has sold or re-pledged to counterparties as collateral. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:CustomerSecuritiesForWhichEntityHasRightToSellOrRepledgeFairValueOfSecuritiesSoldOrRepledged |