cm:Concept: us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleFactsAndCircumstancesLeadingToImpairment
| Impaired Assets to be Disposed of by Method Other than Sale, Facts and Circumstances Leading to Impairment |
| us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleFactsAndCircumstancesLeadingToImpairment |
| A description of the facts and circumstances leading to the impairment of the long-lived asset to be disposed of by a method other than sale. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleFactsAndCircumstancesLeadingToImpairment |