cm:Concept: us-gaap:GainLossOnSaleOfCommodityContracts
| Gain (Loss) on Sale of Commodity Contracts |
| us-gaap:GainLossOnSaleOfCommodityContracts |
| The difference between the book value and the sale price of agreements to purchase or sell mineral resources, energy, and agricultural products at some future point. This element refers to the gain (loss) included in earnings and not to the cash proceeds. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GainLossOnSaleOfCommodityContracts |