| Standard label: | Coal Industry Retiree Health Benefit Act of 1992 [Abstract] |
| Name: | us-gaap:CoalIndustryRetireeHealthBenefitActOf1992Abstract |
| Documentation: | |
| Object type: | cm:Abstract |
| Data type: | Text/String (xbrli:stringItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:CoalIndustryRetireeHealthBenefitActOf1992Abstract |
| Label | Role | Language |
| Coal Industry Retiree Health Benefit Act of 1992 [Abstract] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |