cm:Member: us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember
       
          
          | Change in Accounting Method Accounted for as Change in Estimate [Member] | 
       
       
          
          | us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember | 
       
       
          
          | A change from one acceptable accounting method to another based upon a revision in estimated future benefits or obligations. | 
       
       
          
          | cm:Member | 
       
       
          
          | [Member] (nonnum:domainItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | true | 
       
       
          
          | us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember |