cm:Level1TextBlock: us-gaap:CashCashEquivalentsAndMarketableSecuritiesTextBlock
       
          
          | Cash, Cash Equivalents, and Marketable Securities [Text Block] | 
       
       
          
          | us-gaap:CashCashEquivalentsAndMarketableSecuritiesTextBlock | 
       
       
          
          | The entire disclosure of cash, cash equivalents, and debt and equity securities, including any unrealized or realized gain (loss). | 
       
       
          
          | cm:Level1TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:CashCashEquivalentsAndMarketableSecuritiesTextBlock | 
       
       
          
          | CashCashEquivalentsAndMarketableSecuritiesDisclosure |