cm:Concept: us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale
       
          
          | Proceeds from Collection of Retained Interest in Securitized Receivables categorized as Available-for-sale | 
       
       
          
          | us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale | 
       
       
          
          | Amount of cash inflow from collection on beneficial interest in securitization of loan receivable measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivablesCategorizedAsAvailableForSale |