cm:Level2TextBlock: us-gaap:AssetRetirementObligationsPolicy
| Asset Retirement Obligation [Policy Text Block] |
| us-gaap:AssetRetirementObligationsPolicy |
| Disclosure of accounting policy for legal obligation associated with retirement of long-lived asset that results from acquisition, construction, or development or from normal operation of long-lived asset. Excludes environmental remediation liability from improper or other-than-normal operation of long-lived asset, obligation arising in connection with leased property that meets definition of lease payments or variable lease payments and from plan to sell or otherwise dispose of a long-lived asset. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
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| us-gaap:AssetRetirementObligationsPolicy |