cm:Level2TextBlock: us-gaap:ComparabilityOfPriorYearFinancialData
       
          
          | Comparability of Prior Year Financial Data, Policy [Policy Text Block] | 
       
       
          
          | us-gaap:ComparabilityOfPriorYearFinancialData | 
       
       
          
          | Disclosure of accounting policy for reporting any exceptions to the  comparability of prior year financial data with data shown for the most recent accounting period. | 
       
       
          
          | cm:Level2TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ComparabilityOfPriorYearFinancialData |