| Standard label: | Unrealized Gain (Loss) on Energy Contracts |
| Name: | us-gaap:UnrealizedGainLossOnEnergyContracts |
| Documentation: | The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open agreements to purchase or sell energy at some future point, held at each balance sheet date, that was included in earnings for the period. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | For Period (duration) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:UnrealizedGainLossOnEnergyContracts |
| Label | Role | Language |
| Unrealized Gain (Loss) on Energy Contracts | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 230 10 45 28 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 230 |
| Part Of Roll Up: |
| us-gaap:UnrealizedGainLossOnDerivativesAndCommodityContracts |