cm:Concept: us-gaap:IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple
       
          
          | Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle | 
       
          
          | us-gaap:IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple | 
       
          
          | Amount of cumulative tax effect on beginning retained earnings from change in accounting principle. | 
       
          
          | cm:Concept | 
       
          
          | Monetary (xbrli:monetaryItemType) | 
       
          
          | For Period (duration) | 
       
          
          | Debit | 
       
          
          | false | 
       
          
          | us-gaap:IncomeTaxEffectsAllocatedDirectlyToEquityCumulativeEffectOfChangeInAccountingPrinciple |