UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenues	$ (1,078.9)	$ (1,342.5)	$ (3,711.7)	$ (3,355.8)
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	803.7	838.4	2,512.3	2,363.0
Depreciation, depletion and amortization	82.3	80.7	239.2	227.4
Asset retirement obligation expenses	15.4	13.1	46.3	40.8
Selling and administrative expenses	21.5	19.6	66.0	64.5
Restructuring charges	0.9	1.0	3.0	2.8
Other operating (income) loss:
Net gain on disposals	(1.4)	(5.0)	(8.5)	(22.7)
Asset impairment	0.0	1.7	2.0	1.7
Provision for NARM and Shoal Creek loss	3.3	0.0	37.0	0.0
Income from equity affiliates	(5.6)	(27.5)	(9.7)	(120.9)
Operating profit	158.8	420.5	824.1	799.2
Interest expense	13.8	33.8	45.5	110.8
Net loss on early debt extinguishment	0.0	8.7	8.8	34.5
Interest income	(20.3)	(4.9)	(56.5)	(6.3)
Net periodic benefit credit, excluding service cost	(10.0)	(12.2)	(29.4)	(36.7)
Income from continuing operations before income taxes	175.3	395.1	855.7	696.9
Income tax provision	46.5	10.7	238.7	21.0
Income from continuing operations, net of income taxes	128.8	384.4	617.0	675.9
Income (loss) from discontinued operations, net of income taxes	2.5	(0.8)	(0.1)	(2.3)
Net income	131.3	383.6	616.9	673.6
Less: Net income attributable to noncontrolling interests	11.4	8.5	49.3	8.5
Net income attributable to common stockholders	$ 119.9	$ 375.1	$ 567.6	$ 665.1
Income from continuing operations:
Basic income per share	$ 0.88	$ 2.61	$ 4.06	$ 4.72
Diluted income per share	0.80	2.34	3.68	4.33
Net income attributable to common stockholders:
Basic income per share	0.90	2.60	4.05	4.70
Diluted income per share	$ 0.82	$ 2.33	$ 3.68	$ 4.31