cm:Concept: us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment
       
          
          | Retained Earnings, Effective Date of New Retained Earnings Account Established after Readjustment | 
       
          
          | us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment | 
       
          
          | Effective date of a new retained earnings account established after a readjustment (for example, but not limited to, quasi-reorganization), in CCYY-MM-DD format. | 
       
          
          | cm:Concept | 
       
          
          | Date (xbrli:dateItemType) | 
       
          
          | For Period (duration) | 
       
          
          | (no balance type) | 
       
          
          | false | 
       
          
          | us-gaap:RetainedEarningsEffectiveDatesOfNewRetainedEarningsAccountEstablishedAfterReadjustment |