Principles of Consolidation and Nature of Operations (Narrative) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2024 USD ($)	Dec. 31, 2025 USD ($) a segment	Dec. 31, 2024 USD ($) a	Dec. 31, 2023 USD ($)
Long-term Purchase Commitment [Line Items]
Number of operating segments | segment		3
Number of reportable segments | segment		3
Long term contracts percentage		100.00%
Business interruption insurance recoveries		$ 0	$ 13,612
Acquisitions of mineral and royalty interests		$ 4,661	$ 713
Gross acres | a		10,500	13,700
Net royalty acres | a		400	600
Gross acres of mineral and royalty interest | a		208,000.0
Net royalty acres of mineral and royalty interest | a		64,400
Assets held for sale		$ 12,774	$ 14,159
Proceeds from the sale of assets		286	5,146
Settlements		7,804	0
Gain on settlement of excess funding liability		3,590	0
Excess funding liability		5,450	0
Prepaid profit sharing		11,529	0
Pension Plan
Long-term Purchase Commitment [Line Items]
Settlements		7,804	0
Excess funding of terminated pension plan		10,900
Gain on settlement of excess funding liability		3,600
Payment of excess funding liability		5,500
Excess funding liability		5,400
Pension Plan | Combined Plan And Falkirk Defined Benefit Plan
Long-term Purchase Commitment [Line Items]
Remaining funds		14,600
Prepaid profit sharing		11,500
Prepaid profit sharing and the long-term portion		3,100
Contract Mining customer | Draglines Classified As Assets Held For Sale
Long-term Purchase Commitment [Line Items]
Proceeds from the sale of assets		100
Minerals and Royalties
Long-term Purchase Commitment [Line Items]
Sale of land	$ 7,000
Gain in the minerals management segment	$ 4,500
Eiger, LLC
Long-term Purchase Commitment [Line Items]
Equity method investment in Eiger Resources		33,723	19,147	$ 2,800
Eiger, LLC | Minerals and Royalties
Long-term Purchase Commitment [Line Items]
Equity method investment in Eiger Resources		$ 33,700	$ 19,100
Variable interest entity, ownership percentage (less than)		20.00%	20.00%