CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenues	$ 4,981.9	$ 3,318.3	$ 2,881.1
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	3,290.8	2,553.1	2,524.9
Depreciation, depletion and amortization	317.6	308.7	346.0
Asset retirement obligation expenses	49.4	44.7	45.7
Selling and administrative expenses	88.8	84.9	99.5
Restructuring charges	2.9	8.3	37.9
Transaction costs related to joint ventures	0.0	0.0	23.1
Other operating (income) loss:
Net gain on disposals	(29.2)	(31.5)	(15.2)
Asset impairment	11.2	0.0	1,487.4
(Income) loss from equity affiliates	(131.2)	(82.1)	60.1
Operating profit (loss)	1,381.6	432.2	(1,728.3)
Interest expense	140.3	183.4	139.8
Net loss (gain) on early debt extinguishment	57.9	(33.2)	0.0
Interest income	(18.4)	(6.5)	(9.4)
Amortization of prior service credit	(49.0)	(38.3)	(1.8)
Net mark-to-market adjustment on actuarially determined liabilities	(27.8)	(43.4)	(5.1)
Income (loss) from continuing operations before income taxes	1,278.6	370.2	(1,851.8)
Income tax (benefit) provision	(38.8)	22.8	8.0
Income (loss) from continuing operations, net of income taxes	1,317.4	347.4	(1,859.8)
Income (loss) from discontinued operations, net of income taxes	1.7	24.0	(14.0)
Net income (loss)	1,319.1	371.4	(1,873.8)
Less: Net income (loss) attributable to noncontrolling interests	22.0	11.3	(3.5)
Net income (loss) attributable to common stockholders	$ 1,297.1	$ 360.1	$ (1,870.3)
Income (loss) from continuing operations:
Basic income (loss) per share	$ 9.12	$ 3.03	$ (18.99)
Diluted income (loss) per share	8.29	3.00	(18.99)
Net income (loss) attributable to common stockholders:
Basic income (loss) per share	9.13	3.24	(19.14)
Diluted income (loss) per share	$ 8.31	$ 3.22	$ (19.14)