cm:Concept: us-gaap:IncreaseDecreaseInOtherFinancialInstrumentsUsedInOperatingActivities
       
          
          | Increase (Decrease) in Other Financial Instruments Used in Operating Activities | 
       
       
          
          | us-gaap:IncreaseDecreaseInOtherFinancialInstrumentsUsedInOperatingActivities | 
       
       
          
          | Amount of increase (decrease) in fair value of other financial instruments used in operating activities. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:IncreaseDecreaseInOtherFinancialInstrumentsUsedInOperatingActivities |