| Standard label: | Asset Retirement Obligation, Legally Restricted Assets, Fair Value |
| Name: | us-gaap:AssetRetirementObligationLegallyRestrictedAssetsFairValue |
| Documentation: | Carrying amount of an asset that is legally restricted for purposes of settling an asset retirement obligation. |
| 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:AssetRetirementObligationLegallyRestrictedAssetsFairValue |
| Label | Role | Language |
| Asset Retirement Obligation, Legally Restricted Assets, Fair Value | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 410 20 50 1 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 410 |