cm:Concept: us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax
       
          
          | Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax | 
       
          
          | us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax | 
       
          
          | Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. | 
       
          
          | cm:Concept | 
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
          
          | For Period (duration) | 
       
          
          | Credit | 
       
          
          | false | 
       
          
          | us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax |