Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Revenues	$ 277,198	$ 237,708
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	92,331	66,506
Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	184,867	171,202
Operating Segments | Utility Coal Mining
Disaggregation of Revenue [Line Items]
Revenues	88,188	68,611
Operating Segments | Contract Mining
Disaggregation of Revenue [Line Items]
Revenues	140,013	119,600
Operating Segments | Minerals and Royalties
Disaggregation of Revenue [Line Items]
Revenues	37,630	34,579
Unallocated Items
Disaggregation of Revenue [Line Items]
Revenues	15,080	17,707
Eliminations
Disaggregation of Revenue [Line Items]
Revenues	$ (3,713)	$ (2,789)