Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Revenues	$ 575,688		$ 2,324,623
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	470,644		1,843,093
Depreciation, depletion and amortization	32,604		122,464
Accretion on asset retirement obligations	7,634		30,209
Amortization of sales contracts, net	796		53,985
Change in fair value of coal derivatives and coal trading activities, net	396		7,222
Asset impairment and mine closure costs	0		0
Losses from disposed operations resulting from Patriot Coal bankruptcy	0		0
Selling, general and administrative expenses	22,836		86,821
Gain on sale of Lone Mountain Processing, Inc.	0		(21,297)
Other operating (income) expense, net	(5,340)		(30,270)
Total operating expenses	529,570		2,092,227
Income (loss) from operations	46,118		232,396
Interest expense, net
Interest expense	(11,241)		(26,905)
Interest and investment income	487		2,649
Interest expense, net	(10,754)		(24,256)
Income (loss) before nonoperating expenses	35,364		208,140
Nonoperating income (expense)
Net loss resulting from early retirement of debt and debt restructuring	0		(2,547)
Reorganization income (loss), net	(759)		(2,398)
Nonoperating Income (Expense)	(759)		(4,945)
Income (loss) before income taxes	34,605		203,195
Provision for (benefit from) income taxes	1,156		(35,255)
Net income (loss)	$ 33,449		$ 238,450
Earnings (loss) per common share
Basic earnings (loss) per common share (in dollars per share)	$ 1.34		$ 10.05
Diluted earnings (loss) per common share (in dollars per share)	$ 1.31		$ 9.84
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	25,002		23,725
Diluted weighted average shares outstanding (in shares)	25,469		24,240
Predecessor
Revenues		$ 1,398,709		$ 2,573,260
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)		1,264,464		2,172,753
Depreciation, depletion and amortization		191,581		379,345
Accretion on asset retirement obligations		24,321		33,680
Amortization of sales contracts, net		(728)		(8,811)
Change in fair value of coal derivatives and coal trading activities, net		2,856		(1,583)
Asset impairment and mine closure costs		129,267		2,628,303
Losses from disposed operations resulting from Patriot Coal bankruptcy		0		116,343
Selling, general and administrative expenses		59,343		98,783
Gain on sale of Lone Mountain Processing, Inc.		0		0
Other operating (income) expense, net		(15,257)		19,510
Total operating expenses		1,655,847		5,438,323
Income (loss) from operations		(257,138)		(2,865,063)
Interest expense, net
Interest expense		(135,888)		(397,979)
Interest and investment income		2,653		4,430
Interest expense, net		(133,235)		(393,549)
Income (loss) before nonoperating expenses		(390,373)		(3,258,612)
Nonoperating income (expense)
Net loss resulting from early retirement of debt and debt restructuring		(2,213)		(27,910)
Reorganization income (loss), net		1,630,041		0
Nonoperating Income (Expense)		1,627,828		(27,910)
Income (loss) before income taxes		1,237,455		(3,286,522)
Provision for (benefit from) income taxes		(4,626)		(373,380)
Net income (loss)		$ 1,242,081		$ (2,913,142)
Earnings (loss) per common share
Basic earnings (loss) per common share (in dollars per share)		$ 58.33		$ (136.86)
Diluted earnings (loss) per common share (in dollars per share)		$ 58.28		$ (136.86)
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)		21,293		21,285
Diluted weighted average shares outstanding (in shares)		21,313		21,285