cm:Concept: us-gaap:AociMarketRiskBenefitInstrumentSpecificCreditRiskAfterTax
       
          
          | AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, after Tax | 
       
       
          
          | us-gaap:AociMarketRiskBenefitInstrumentSpecificCreditRiskAfterTax | 
       
       
          
          | Amount, after tax, of accumulated other comprehensive income (loss) (AOCI) from (increase) decrease in instrument-specific credit risk on contract or contract feature in long-duration contract issued by insurance entity protecting contract holder from other-than-nominal capital market risk and exposing insurance entity to other-than-nominal capital market risk. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | As Of (instant) | 
       
       
          
          | Credit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:AociMarketRiskBenefitInstrumentSpecificCreditRiskAfterTax |