Unaudited Condensed Consolidated Statements of Operations - USD ($) $ in Millions		3 Months Ended			6 Months Ended
	Apr. 01, 2017	Jun. 30, 2018	Jun. 30, 2017	Apr. 01, 2017	Jun. 30, 2018
Other operating (income) loss:
Loss on early debt extinguishment	$ 0.0
Successor
Revenues
Sales		$ 1,137.3	$ 1,059.6		$ 2,406.4
Other revenues		172.1	198.7		365.7
Total revenues		1,309.4	1,258.3		2,772.1
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)		946.5	927.9		2,003.7
Depreciation, depletion and amortization		163.9	148.3		333.5
Asset retirement obligation expenses		13.2	11.0		25.5
Selling and administrative expenses		44.1	34.7		81.1
Other operating (income) loss:
Net loss (gain) on disposals		1.6	(0.5)		(29.0)
Asset impairment		0.0	0.0		0.0
Income from equity affiliates		(25.2)	(15.7)		(47.2)
Operating profit		165.3	152.6		404.5
Interest expense		(38.3)	(41.4)		(74.6)
Loss on early debt extinguishment		2.0	0.0		2.0
Interest income		(7.0)	(1.5)		(14.2)
Net periodic benefit costs, excluding service cost		4.6	6.6		9.1
Reorganization items, net		0.0	0.0		(12.8)
Income (loss) from continuing operations before income taxes		127.4	106.1		345.8
Income tax provision (benefit)		7.4	4.7		17.5
Income (loss) from continuing operations, net of income taxes		120.0	101.4		328.3
Loss from discontinued operations, net of income taxes		(3.6)	(2.7)		(4.9)
Net income (loss)		116.4	98.7		323.4
Less: Series A Convertible Preferred Stock dividends		0.0	115.1		102.5
Less: Net income attributable to noncontrolling interests		2.7	3.8		0.6
Net income (loss) attributable to common stockholders		$ 113.7	$ (20.2)		$ 220.3
Income (loss) from continuing operations:
Basic income per share (in dollars per share)		$ 0.94	$ (0.18)		$ 1.78
Diluted income per share (in dollars per share)		0.93	(0.18)		1.76
Net income (loss) attributable to common stockholders:
Basic income per share (in dollars per share)		0.91	(0.21)		1.74
Diluted income per share (in dollars per share)		0.90	(0.21)		1.72
Dividends declared per share (in dollars per share)		$ 0.115	$ 0.000		$ 0.230
Predecessor
Revenues
Sales	0.0			$ 1,081.4
Other revenues	0.0			244.8
Total revenues	0.0			1,326.2
Costs and expenses
Operating costs and expenses (exclusive of items shown separately below)	0.0			950.2
Depreciation, depletion and amortization	0.0			119.9
Asset retirement obligation expenses	0.0			14.6
Selling and administrative expenses	0.0			36.3
Other operating (income) loss:
Net loss (gain) on disposals	0.0			(22.8)
Asset impairment	0.0			30.5
Income from equity affiliates	0.0			(15.0)
Operating profit	0.0			212.5
Interest expense	0.0			(32.9)
Loss on early debt extinguishment	0.0			0.0
Interest income	0.0			(2.7)
Net periodic benefit costs, excluding service cost	0.0			14.4
Reorganization items, net	585.8			627.2
Income (loss) from continuing operations before income taxes	(585.8)			(459.3)
Income tax provision (benefit)	(266.0)			(263.8)
Income (loss) from continuing operations, net of income taxes	(319.8)			(195.5)
Loss from discontinued operations, net of income taxes	(12.1)			(16.2)
Net income (loss)	(331.9)			(211.7)
Less: Series A Convertible Preferred Stock dividends	0.0			0.0
Less: Net income attributable to noncontrolling interests	0.0			4.8
Net income (loss) attributable to common stockholders	$ (331.9)			$ (216.5)
Income (loss) from continuing operations:
Basic income per share (in dollars per share)	$ (17.44)			$ (10.93)
Diluted income per share (in dollars per share)	(17.44)			(10.93)
Net income (loss) attributable to common stockholders:
Basic income per share (in dollars per share)	(18.10)			(11.81)
Diluted income per share (in dollars per share)	(18.10)			(11.81)
Dividends declared per share (in dollars per share)	$ 0			$ 0