Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash Flows from Operating Activities:
Net (Loss) Income	$ (153,216)	$ 286,405	$ 655,892
Adjustments to Reconcile Net (Loss) Income to Net Cash Provided by Operating Activities:
Depreciation, Depletion and Amortization	621,067	223,526	241,317
Gain on Sale of Assets	(7,027)	(6,941)	(8,981)
Stock-Based Compensation	32,918	11,350	10,046
Loss on Debt Extinguishment	11,680	0	2,725
Deferred Income Taxes	(80,971)	8,820	14,121
Loss from Equity Method Investments	15,476	1,326	199
Other Adjustments to Net (Loss) Income	4,411	(371)	1,851
Changes in Operating Assets:
Accounts and Notes Receivable	(64,045)	(2,233)	36,922
Inventories	28,661	(8,018)	(21,540)
Other Current Assets	(4,684)	(444)	(4,673)
Changes in Other Assets	17,783	7,936	(11,725)
Changes in Operating Liabilities:
Accounts Payable	(24,268)	4,570	11,449
Commodity Derivatives, net Liability	0	0	(15,142)
Other Operating Liabilities	(9,144)	(25,420)	3,063
Payments on Asset Retirement Obligations	(36,205)	(30,089)	(22,771)
Changes in Other Liabilities	(46,684)	5,973	(34,804)
Net Cash Provided by Operating Activities	305,752	476,390	857,949
Cash Flows from Investing Activities:
Capital Expenditures	(284,581)	(177,988)	(167,791)
Proceeds from Sales of Assets	7,514	7,396	4,255
Proceeds from Sales of Short-Term Investments	80,165	100,982	122,658
Purchases of Short-Term Investments	(4,802)	(66,963)	(200,870)
Net Cash and Restricted Cash Acquired from Merger	368,726	0	0
Purchase of Arch Tax-Exempt Bonds	(98,225)	0	0
Investments in DTA	(15,733)	0	0
Other Investing Activity	(5,405)	(28,458)	(17,684)
Net Cash Provided by (Used in) Investing Activities	47,659	(165,031)	(259,432)
Cash Flows from Financing Activities:
Payments on Finance Lease Obligations	(12,554)	(10,518)	(25,335)
Proceeds from Long-Term Debt Issuance	114,439	0	0
Payments on Other Debt	(14,118)	(955)	(981)
Shares Withheld for Taxes	(15,619)	(5,126)	(12,831)
Repurchases of Common Stock	(224,264)	(70,879)	(399,379)
Debt-Related Financing Fees	(20,477)	0	(2,779)
Payments of Excise Tax on Share Repurchases	(934)	(3,747)	0
Dividends and Dividend Equivalents Paid	(26,264)	(15,860)	(75,474)
Net Cash Used in Financing Activities	(199,791)	(107,085)	(682,201)
Net Increase (Decrease) in Cash and Cash Equivalents and Restricted Cash	153,620	204,274	(83,684)
Cash and Cash Equivalents and Restricted Cash at Beginning of Period	447,542	243,268	326,952
Cash and Cash Equivalents and Restricted Cash at End of Period	601,162	447,542	243,268
Term Loan B
Cash Flows from Financing Activities:
Repayments of debt	0	0	(63,590)
Second Lien Notes
Cash Flows from Financing Activities:
Repayments of debt	$ 0	$ 0	$ (101,832)