UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenues	$ 890.1	$ 1,042.0	$ 1,827.1	$ 2,025.6
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	789.4	803.9	1,559.6	1,618.1
Depreciation, depletion and amortization	93.4	82.9	185.5	162.7
Asset retirement obligation expenses	13.8	12.9	27.4	25.8
Selling and administrative expenses	23.5	22.1	47.1	44.1
Restructuring charges	3.5	0.1	5.2	0.2
Transaction costs related to business combinations	18.8	0.0	21.2	0.0
Other operating (income) loss:
Net gain on disposals	(14.8)	(7.5)	(20.0)	(9.6)
Provision for NARM loss	0.0	1.9	0.0	3.7
Shoal Creek insurance recovery	0.0	(109.5)	0.0	(109.5)
Loss from equity affiliates	0.9	1.3	7.6	5.0
Operating (loss) profit	(38.4)	233.9	(6.5)	285.1
Interest expense, net of capitalized interest	11.1	10.7	22.6	25.4
Interest income	(13.8)	(16.8)	(29.2)	(36.0)
Net periodic benefit credit, excluding service cost	(7.4)	(10.2)	(14.8)	(20.3)
(Loss) income from continuing operations before income taxes	(28.3)	250.2	14.9	316.0
Income tax (benefit) provision	(2.7)	39.4	2.2	59.5
(Loss) income from continuing operations, net of income taxes	(25.6)	210.8	12.7	256.5
Loss from discontinued operations, net of income taxes	(0.4)	(1.6)	(0.7)	(2.3)
Net (loss) income	(26.0)	209.2	12.0	254.2
Less: Net income attributable to noncontrolling interests	1.6	9.8	5.2	15.2
Net (loss) income attributable to common stockholders	$ (27.6)	$ 199.4	$ 6.8	$ 239.0
(Loss) income from continuing operations:
Basic (loss) income per share	$ (0.22)	$ 1.59	$ 0.06	$ 1.90
Diluted (loss) income per share	(0.22)	1.43	0.06	1.72
Net (loss) income attributable to common stockholders:
Basic (loss) income per share	(0.23)	1.58	0.06	1.88
Diluted (loss) income per share	$ (0.23)	$ 1.42	$ 0.06	$ 1.70