cm:Concept: us-gaap:ImpairedLongLivedAssetsHeldAndUsedMethodForDeterminingFairValue
| Impaired Long-Lived Assets Held and Used, Method for Determining Fair Value |
| us-gaap:ImpairedLongLivedAssetsHeldAndUsedMethodForDeterminingFairValue |
| A description of how an entity determined the fair value of the long-lived asset they are holding and using, for example, whether based on a quoted market price, prices for similar assets, or another valuation technique. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ImpairedLongLivedAssetsHeldAndUsedMethodForDeterminingFairValue |