CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017
Successor
Revenues:
Sales	$ 351,788,000	$ 85,415,000		$ 592,844,000
Other revenues	11,582,000	6,059,000		24,490,000
Total revenues	363,370,000	91,474,000		617,334,000
Costs and expenses:
Cost of sales (exclusive of items shown separately below)	160,152,000	103,866,000		266,296,000
Cost of other revenues (exclusive of items shown separately below)	7,795,000	5,126,000		15,974,000
Depreciation and depletion	19,650,000	15,821,000		34,232,000
Selling, general and administrative	8,660,000	5,815,000		13,830,000
Other postretirement benefits	0	0		0
Restructuring costs	0	0		0
Transaction and other costs	3,837,000	10,475,000		12,873,000
Total costs and expenses	200,094,000	141,103,000		343,205,000
Operating income (loss)	163,276,000	(49,629,000)		274,129,000
Interest expense, net	(642,000)	(434,000)		(1,250,000)
Reorganization items, net	0	0		0
Income (loss) before income tax expense	162,634,000	(50,063,000)		272,879,000
Income tax expense	32,769,000	0		34,706,000
Net income (loss)	$ 129,865,000	$ (50,063,000)		$ 238,173,000
Basic and diluted net income per share:
Net income (loss) per share—basic and diluted (in dollars per share)	$ 2.46	$ (0.95)		$ 4.52
Weighted average number of shares outstanding—basic and diluted (in shares)	52,721	52,640		52,702
Dividends per share (in dollars per share)	$ 0.05	$ 0.00		$ 3.61
Predecessor
Revenues:
Sales			$ 65,154,000
Other revenues			6,229,000
Total revenues			71,383,000
Costs and expenses:
Cost of sales (exclusive of items shown separately below)			72,297,000
Cost of other revenues (exclusive of items shown separately below)			4,698,000
Depreciation and depletion			28,958,000
Selling, general and administrative			9,008,000
Other postretirement benefits			6,160,000
Restructuring costs			3,418,000
Transaction and other costs			0
Total costs and expenses			124,539,000
Operating income (loss)			(53,156,000)
Interest expense, net			(16,562,000)
Reorganization items, net	$ 7,920,000		7,920,000
Income (loss) before income tax expense			(61,798,000)
Income tax expense			18,000
Net income (loss)			$ (61,816,000)