UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Revenue	$ 1,364.0	$ 691.4
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	846.6	699.0
Depreciation, depletion and amortization	76.3	72.9
Asset retirement obligation expenses	15.4	15.0
Selling and administrative expenses	22.8	23.1
Restructuring charges	0.1	1.6
Other operating income:
Net gain on disposals	(1.9)	(4.9)
Asset impairment	2.0	0.0
Income from equity affiliates	(1.8)	(44.7)
Operating profit (loss)	404.5	(70.6)
Interest expense	18.4	39.4
Net loss on early debt extinguishment	6.8	23.5
Interest income	(13.1)	(0.5)
Net periodic benefit credit, excluding service cost	(9.7)	(12.2)
Income (loss) from continuing operations before income taxes	402.1	(120.8)
Income tax provision (benefit)	118.0	(1.0)
Income (loss) from continuing operations, net of income taxes	284.1	(119.8)
Loss from discontinued operations, net of income taxes	(1.3)	(0.8)
Net income (loss)	282.8	(120.6)
Less: Net income (loss) attributable to noncontrolling interests	14.3	(1.1)
Net income (loss) attributable to common stockholders	$ 268.5	$ (119.5)
Income (loss) from continuing operations:
Basic income (loss) per share	$ 1.87	$ (0.87)
Diluted income (loss) per share	1.69	(0.87)
Net income (loss) attributable to common stockholders:
Basic income (loss) per share	1.86	(0.88)
Diluted income (loss) per share	$ 1.68	$ (0.88)