cm:Level3TextBlock: us-gaap:NetInvestmentInLeaseAllowanceForCreditLossTableTextBlock
       
          
          | Net Investment in Lease, Allowance for Credit Loss [Table Text Block] | 
       
       
          
          | us-gaap:NetInvestmentInLeaseAllowanceForCreditLossTableTextBlock | 
       
       
          
          | Tabular disclosure of allowance for credit loss on net investment in sales-type and direct financing leases. | 
       
       
          
          | cm:Level3TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:NetInvestmentInLeaseAllowanceForCreditLossTableTextBlock |