Details for Selection
| Standard label: | Royalty Revenue from Coal |
| Name: | us-gaap:RoyaltyRevenueFromCoal |
| Documentation: | Revenue earned during the period by the entity for rights granted to another party under coal mineral leases. |
| Commentary: | |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | For period (duration) |
| Balance type: | Credit |
| Object class: | [Concept] |