| Standard label: | Gas Purchase Contract, Fair Value Disclosure |
| Name: | us-gaap:GasPurchaseContractFairValueDisclosure |
| Documentation: | Fair value of contract to purchase gas. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Debit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:GasPurchaseContractFairValueDisclosure |
| Label | Role | Language |
| Gas Purchase Contract, Fair Value Disclosure | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 932 330 35 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 932 |
| Part Of Roll Up: |
| us-gaap:AssetsFairValueDisclosure |