cm:Concept: us-gaap:IncreaseDecreaseInFuturePolicyBenefitReservesAndOtherInsuranceLiabilities
       
          
          | Increase (Decrease) in Future Policy Benefit Reserves and Other Insurance Liabilities | 
       
       
          
          | us-gaap:IncreaseDecreaseInFuturePolicyBenefitReservesAndOtherInsuranceLiabilities | 
       
       
          
          | Amount of increase (decrease) in estimated future policy benefit obligations under insurance contracts, and obligations under insurance contracts classified as other. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:IncreaseDecreaseInFuturePolicyBenefitReservesAndOtherInsuranceLiabilities |