cm:Concept: us-gaap:LongTermContractForPurchaseOfElectricPowerInterestIncludedInContractCharges
| Long-term Contract for Purchase of Electric Power, Interest Included in Contract Charges |
| us-gaap:LongTermContractForPurchaseOfElectricPowerInterestIncludedInContractCharges |
| The allocable portion of interest included in charges under a long-term contract to purchase electric power. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:LongTermContractForPurchaseOfElectricPowerInterestIncludedInContractCharges |