Inventories (Inventory) (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Inventory Disclosure [Abstract]
Coal	$ 24,585	$ 27,076
Mining supplies	73,858	67,532
Total inventories	$ 98,443	$ 94,608

Amount before valuation and LIFO reserves of other supplies used within the manufacturing or production process expected to be consumed within one year or operating cycle, if longer.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Name:	us-gaap_OtherInventorySupplies
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant