cm:Level3TextBlock: us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock
       
          
          | Activity in Affordable Housing Program Obligation [Table Text Block] | 
       
       
          
          | us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock | 
       
       
          
          | Tabular disclosure of the activity in the Affordable Housing Program (AHP) obligation. | 
       
       
          
          | cm:Level3TextBlock | 
       
       
          
          | Text Block (HTML) (nonnum:textBlockItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ScheduleOfActivityInAffordableHousingProgramObligationTableTextBlock |