cm:Concept: us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest
       
          
          | Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, before Tax, after Reclassification Adjustment, Attributable to Noncontrolling Interest | 
       
       
          
          | us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest | 
       
       
          
          | Amount, before tax, after reclassification adjustment, of gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option, attributable to noncontrolling interest. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionBeforeTaxAfterReclassificationAdjustmentAttributableToNoncontrollingInterest |