cm:Concept: us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries
       
          
          | Proceeds from Divestiture of Interest in Consolidated Subsidiaries | 
       
       
          
          | us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries | 
       
       
          
          | The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or the sale of investment in consolidated subsidiaries (generally greater than 50 percent). | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries |