| Standard label: | Energy Related Inventory, Coal |
| Name: | us-gaap:EnergyRelatedInventoryCoal |
| Documentation: | Carrying amount as of the balance sheet date of coal, which is a combustible rock or minerals which are extracted from the ground and used as fuel. |
| 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:EnergyRelatedInventoryCoal |
| Label | Role | Language |
| Energy Related Inventory, Coal | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 210 10 S99 1 (SX 210.5-02.6(a)) | http://fasb.org/us-gaap/role/ref/legacyRef | 210 |
| Part Of Roll Up: |
| us-gaap:EnergyRelatedInventory |