cm:Concept: us-gaap:DescriptionOfReclassificationOfPriceRiskCashFlowHedgeGainLoss
| Description of Reclassification of Price Risk Cash Flow Hedge Gain (Loss) |
| us-gaap:DescriptionOfReclassificationOfPriceRiskCashFlowHedgeGainLoss |
| Description of the transactions or other events that will result in the reclassification into earnings of gains or losses reported in accumulated other comprehensive income. Includes time period over which gains or losses will be reclassified to earnings. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfReclassificationOfPriceRiskCashFlowHedgeGainLoss |