cm:Concept: us-gaap:IncreaseDecreaseInPayablesToBrokerDealers
       
          
          | Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations | 
       
       
          
          | us-gaap:IncreaseDecreaseInPayablesToBrokerDealers | 
       
       
          
          | The increase (decrease) during the reporting period in the aggregate amount of obligations incurred arising from transactions with broker-dealers, such as amounts due on margin and unsettled cash transactions; includes payables to brokers, dealers and clearing organizations. | 
       
       
          
          | cm:Concept | 
       
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
       
          
          | For Period (duration) | 
       
       
          
          | Debit | 
       
       
          
          | false | 
       
       
          
          | us-gaap:IncreaseDecreaseInPayablesToBrokerDealers |