cm:Concept: us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold
       
          
          | Resale Agreements, Collateral Rights in Event of Default Related to Securities to be Resold | 
       
       
          
          | us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold | 
       
       
          
          | This describes the policy with regards to collateral in the event of a default by the counter party of a resale agreement. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Text/String (xbrli:stringItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | (no balance type) | 
       
       
          
          | false | 
       
       
          
          | us-gaap:ResaleAgreementsCollateralRightsInEventOfDefaultRelatedToSecuritiesToBeResold |