cm:Concept: us-gaap:IncreaseDecreaseInUnderEnergyRecovery
| Increase (Decrease) in under Energy Recovery |
| us-gaap:IncreaseDecreaseInUnderEnergyRecovery |
| The change during the reporting period in the value of the liability created by an under-recovery. An under-recovery means that the basic energy product price based on the daily product price and exchange rate is more than the basic fuel price used in the calculation of the monthly retail energy product. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:IncreaseDecreaseInUnderEnergyRecovery |