| Standard label: | Gas Purchase Payable |
| Name: | us-gaap:GasPurchasePayableCurrentAndNoncurrent |
| Documentation: | Carrying value as of the balance sheet date of obligations incurred and payable for purchases of natural gas. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:GasPurchasePayableCurrentAndNoncurrent |
| Label | Role | Language |
| Gas Purchase Payable | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 942 210 S99 1 (SX 210.9-03.15(5)) | http://fasb.org/us-gaap/role/ref/legacyRef | 942 |
| FASB Accounting Standards Codification 944 210 S99 1 (SX 210.7-03.15(a)) | http://fasb.org/us-gaap/role/ref/legacyRef | 944 |