cm:Concept: us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable
       
          
          | Proceeds from Sale and Collection of Mortgage Notes Receivable | 
       
       
          
          | us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable | 
       
       
          
          | The cash inflow from proceeds from sale of receivables arising from the mortgage note on real estate; includes collections on mortgage notes receivable that are not classified as operating cash flows. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable |