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, 2015	Dec. 31, 2014
Predecessor [Member]
Revenues		$ 1,398,709	$ 2,573,260	$ 2,937,119
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)		1,264,464	2,172,753	2,533,284
Depreciation, depletion and amortization		191,581	379,345	418,748
Accretion on asset retirement obligations		24,321	33,680	32,909
Amortization of sales contracts, net		(728)	(8,811)	(13,187)
Change in fair value of coal derivatives and coal trading activities, net		2,856	(1,583)	(3,686)
Asset impairment and mine closure costs		129,267	2,628,303	24,113
Losses from disposed operations resulting from Patriot Coal bankruptcy		0	116,343	0
Selling, general and administrative expenses		59,343	98,783	114,223
Other operating expense (income), net		(15,257)	19,510	(19,754)
Total operating expenses		1,655,847	5,438,323	3,086,650
Income (loss) from operations		(257,138)	(2,865,063)	(149,531)
Interest expense, net
Interest expense		(135,888)	(397,979)	(390,946)
Interest and investment income		2,653	4,430	7,758
Interest expense, net		(133,235)	(393,549)	(383,188)
Income (loss) before nonoperating expenses		(390,373)	(3,258,612)	(532,719)
Nonoperating expense
Net loss resulting from early retirement of debt and debt restructuring		(2,213)	(27,910)	0
Reorganization income (loss), net		1,630,041	0	0
Nonoperating Income (Expense)		1,627,828	(27,910)	0
Income (loss) before income taxes		1,237,455	(3,286,522)	(532,719)
Provision for (benefit from) income taxes		(4,626)	(373,380)	25,634
Net income (loss)		$ 1,242,081	$ (2,913,142)	$ (558,353)
Earnings per common share
Basic earnings per common share (in dollars per share)		$ 58.33	$ (136.86)	$ (26.31)
Diluted earnings per common share (in dollars per share)		$ 58.28	$ (136.86)	$ (26.31)
Weighted average shares outstanding
Basic weighted average shares outstanding		21,293	21,285	21,222
Diluted weighted average shares outstanding		21,313	21,285	21,222
Successor [Member]
Revenues	$ 575,688
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	470,644
Depreciation, depletion and amortization	32,604
Accretion on asset retirement obligations	7,634
Amortization of sales contracts, net	796
Change in fair value of coal derivatives and coal trading activities, net	396
Asset impairment and mine closure costs	0
Losses from disposed operations resulting from Patriot Coal bankruptcy	0
Selling, general and administrative expenses	22,836
Other operating expense (income), net	(5,340)
Total operating expenses	529,570
Income (loss) from operations	46,118
Interest expense, net
Interest expense	(11,241)
Interest and investment income	487
Interest expense, net	(10,754)
Income (loss) before nonoperating expenses	35,364
Nonoperating expense
Net loss resulting from early retirement of debt and debt restructuring	0
Reorganization income (loss), net	(759)
Nonoperating Income (Expense)	(759)
Income (loss) before income taxes	34,605
Provision for (benefit from) income taxes	1,156
Net income (loss)	$ 33,449
Earnings per common share
Basic earnings per common share (in dollars per share)	$ 1.34
Diluted earnings per common share (in dollars per share)	$ 1.31
Weighted average shares outstanding
Basic weighted average shares outstanding	25,002
Diluted weighted average shares outstanding	25,469