cm:Concept: us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleCarryingValueOfAsset
| Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset |
| us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleCarryingValueOfAsset |
| The carrying amount on the books of the entity of the impaired asset to be disposed of by a method other than sale. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleCarryingValueOfAsset |