| Standard label: | Plant Retirement and Abandonment, Policy [Policy Text Block] |
| Name: | us-gaap:PlantRetirementAndAbandonmentPolicy |
| Documentation: | Disclosure of accounting policy for plant retirement and for abandonment (under construction or in use) in regulated industries when abandonment becomes probable. Any difference between the new asset and the asset cost is recognized as a loss in the income statement. May also indicate the discount rate used in the calculation of present value of recoverable abandoned assets. |
| Object type: | cm:Level2TextBlock |
| Data type: | Text Block (HTML) (nonnum:textBlockItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:PlantRetirementAndAbandonmentPolicy |
| Label | Role | Language |
| Plant Retirement and Abandonment, Policy [Policy Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 235 10 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 235 |
| FASB Accounting Standards Codification 980 360 35 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |
| FASB Accounting Standards Codification 980 360 35 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |
| FASB Accounting Standards Codification 980 360 35 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |