cm:Concept: us-gaap:DescriptionOfTypesOfForeignCurrencyDerivativesNotDesignatedAsHedgingInstrumentsHeld
       
          
          | Description of Types of Foreign Currency Derivatives Not Designated as Hedging Instruments Held | 
       
       
          
          | us-gaap:DescriptionOfTypesOfForeignCurrencyDerivativesNotDesignatedAsHedgingInstrumentsHeld | 
       
       
          
          | Description of the types of foreign currency derivative instruments not designated as hedging instruments. For example, forwards, options, and so forth. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Text/String (xbrli:stringItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:DescriptionOfTypesOfForeignCurrencyDerivativesNotDesignatedAsHedgingInstrumentsHeld |