cm:Concept: us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent
       
          
          | Deferred Compensation Share-based Arrangements, Liability, Current | 
       
       
          
          | us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent | 
       
       
          
          | Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer). | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:DeferredCompensationShareBasedArrangementsLiabilityCurrent |