cm:Concept: us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges
| Gain (Loss) on Sale of Assets and Asset Impairment Charges |
| us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges |
| Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges |