cm:Level2TextBlock: us-gaap:UtilityRevenueAndExpenseRecognitionPolicy
| Utility, Revenue and Expense Recognition, Policy [Policy Text Block] |
| us-gaap:UtilityRevenueAndExpenseRecognitionPolicy |
| Disclosure of accounting policies and anticipated effects of regulatory rulings and on rate-setting regarding revenues and expenses incurred and recovered, including billed and unbilled revenues, revenues collected subject to refund, taxes collected from customers and remitted to governmental authorities, and postretirement benefits. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:UtilityRevenueAndExpenseRecognitionPolicy |