Supplemental Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 550,305		$ 688,544	$ 1,398,709	$ 2,010,011
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	450,427		540,192	1,288,785	1,668,766
Depreciation, depletion and amortization	69,423		103,965	191,581	306,211
Amortization of acquired sales contracts, net	104		(1,994)	(728)	(7,028)
Change in fair value of coal derivatives and coal trading activities, net	488		(3,559)	2,856	(1,128)
Asset impairment and mine closure costs	46	$ 129,300	2,120,292	129,267	2,139,438
Losses from disposed operations resulting from Patriot Coal bankruptcy	0		149,314	0	149,314
Selling, general and administrative expenses	20,498		25,731	59,343	72,604
Other operating (income) expense, net	(2,476)		(8,625)	(15,257)	7,864
Total operating expenses	538,510		2,925,316	1,655,847	4,336,041
Income from investment in subsidiaries	0		0	0	0
Income (loss) from operations	11,795		(2,236,772)	(257,138)	(2,326,030)
Interest expense, net
Interest expense (contractual interest of $101,520 and $300,852 for the three and nine months ended September 30, 2016)	(46,164)		(99,759)	(135,888)	(298,585)
Interest and investment income	582		672	2,653	4,007
Interest expense, net	(45,582)		(99,087)	(133,235)	(294,578)
Nonoperating expense
Expenses related to proposed debt restructuring	0		(7,482)	(2,213)	(11,498)
Reorganization items, net	(20,904)		0	(46,050)	0
Nonoperating income (expense)	(20,904)		(7,482)	(48,263)	(11,498)
Loss before income taxes	(54,691)		(2,343,341)	(438,636)	(2,632,106)
Benefit from income taxes	(3,270)		(343,865)	(4,626)	(351,332)
Net loss	(51,421)		(1,999,476)	(434,010)	(2,280,774)
Total comprehensive income (loss)	(49,765)		(2,000,570)	(433,901)	(2,278,048)
Contractual interest	101,520			300,852
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	0		0	0	0
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	(604)		(490)	(1,698)	(2,171)
Depreciation, depletion and amortization	0		0	0	0
Amortization of acquired sales contracts, net	0		0	0	0
Change in fair value of coal derivatives and coal trading activities, net	0		0	0	0
Asset impairment and mine closure costs	0		0	0	0
Losses from disposed operations resulting from Patriot Coal bankruptcy			0		0
Selling, general and administrative expenses	(391)		(542)	(1,101)	(1,561)
Other operating (income) expense, net	995		1,032	2,799	3,732
Total operating expenses	0		0	0	0
Income from investment in subsidiaries	(45,675)		2,025,900	157,279	2,035,313
Income (loss) from operations	(45,675)		2,025,900	157,279	2,035,313
Interest expense, net
Interest expense (contractual interest of $101,520 and $300,852 for the three and nine months ended September 30, 2016)	30,801		28,473	90,956	82,675
Interest and investment income	(30,801)		(28,473)	(90,956)	(82,675)
Interest expense, net	0		0	0	0
Nonoperating expense
Expenses related to proposed debt restructuring	0		0	0	0
Reorganization items, net	0			0
Nonoperating income (expense)	0			0
Loss before income taxes	(45,675)		2,025,900	157,279	2,035,313
Benefit from income taxes	0		0	0	0
Net loss	(45,675)		2,025,900	157,279	2,035,313
Total comprehensive income (loss)	(47,499)		2,026,924	159,310	2,033,259
Parent/Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	0		0	0	0
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	4,927		3,211	10,463	16,589
Depreciation, depletion and amortization	695		896	2,188	2,969
Amortization of acquired sales contracts, net	0		0	0	0
Change in fair value of coal derivatives and coal trading activities, net	0		0	0	0
Asset impairment and mine closure costs	0		21,292	6,330	22,517
Losses from disposed operations resulting from Patriot Coal bankruptcy			149,314		149,314
Selling, general and administrative expenses	14,241		18,059	40,738	50,664
Other operating (income) expense, net	(1,599)		3,503	(6,151)	7,065
Total operating expenses	18,264		196,275	53,568	249,118
Income from investment in subsidiaries	45,675		(2,025,900)	(157,279)	(2,035,313)
Income (loss) from operations	27,411		(2,222,175)	(210,847)	(2,284,431)
Interest expense, net
Interest expense (contractual interest of $101,520 and $300,852 for the three and nine months ended September 30, 2016)	(68,022)		(120,404)	(200,387)	(357,690)
Interest and investment income	6,850		6,710	20,884	21,457
Interest expense, net	(61,172)		(113,694)	(179,503)	(336,233)
Nonoperating expense
Expenses related to proposed debt restructuring	0		(7,482)	(2,213)	(11,498)
Reorganization items, net	(20,904)			(46,050)
Nonoperating income (expense)	(20,904)			(48,263)
Loss before income taxes	(54,665)		(2,343,351)	(438,613)	(2,632,162)
Benefit from income taxes	(3,244)		(343,875)	(4,603)	(351,388)
Net loss	(51,421)		(1,999,476)	(434,010)	(2,280,774)
Total comprehensive income (loss)	(49,765)		(2,000,570)	(433,901)	(2,278,048)
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	550,305		688,544	1,398,709	2,010,011
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	446,104		537,471	1,280,020	1,654,348
Depreciation, depletion and amortization	68,728		103,069	189,393	303,240
Amortization of acquired sales contracts, net	104		(1,994)	(728)	(7,028)
Change in fair value of coal derivatives and coal trading activities, net	488		(3,559)	2,856	(1,128)
Asset impairment and mine closure costs	46		2,099,000	122,937	2,116,921
Losses from disposed operations resulting from Patriot Coal bankruptcy			0		0
Selling, general and administrative expenses	5,285		6,725	15,936	19,239
Other operating (income) expense, net	(1,001)		(12,343)	(9,268)	417
Total operating expenses	519,754		2,728,369	1,601,146	4,086,009
Income from investment in subsidiaries	0		0	0	0
Income (loss) from operations	30,551		(2,039,825)	(202,437)	(2,075,998)
Interest expense, net
Interest expense (contractual interest of $101,520 and $300,852 for the three and nine months ended September 30, 2016)	(6,705)		(6,629)	(19,678)	(19,969)
Interest and investment income	23,130		20,781	68,988	60,811
Interest expense, net	16,425		14,152	49,310	40,842
Nonoperating expense
Expenses related to proposed debt restructuring	0		0	0	0
Reorganization items, net	0			0
Nonoperating income (expense)	0			0
Loss before income taxes	46,976		(2,025,673)	(153,127)	(2,035,156)
Benefit from income taxes	0		0	0	0
Net loss	46,976		(2,025,673)	(153,127)	(2,035,156)
Total comprehensive income (loss)	48,800		(2,026,697)	(155,158)	(2,033,102)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	0		0	0	0
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	0		0	0	0
Depreciation, depletion and amortization	0		0	0	2
Amortization of acquired sales contracts, net	0		0	0	0
Change in fair value of coal derivatives and coal trading activities, net	0		0	0	0
Asset impairment and mine closure costs	0		0	0	0
Losses from disposed operations resulting from Patriot Coal bankruptcy			0		0
Selling, general and administrative expenses	1,363		1,489	3,770	4,262
Other operating (income) expense, net	(871)		(817)	(2,637)	(3,350)
Total operating expenses	492		672	1,133	914
Income from investment in subsidiaries	0		0	0	0
Income (loss) from operations	(492)		(672)	(1,133)	(914)
Interest expense, net
Interest expense (contractual interest of $101,520 and $300,852 for the three and nine months ended September 30, 2016)	(2,238)		(1,199)	(6,779)	(3,601)
Interest and investment income	1,403		1,654	3,737	4,414
Interest expense, net	(835)		455	(3,042)	813
Nonoperating expense
Expenses related to proposed debt restructuring	0		0	0	0
Reorganization items, net	0			0
Nonoperating income (expense)	0			0
Loss before income taxes	(1,327)		(217)	(4,175)	(101)
Benefit from income taxes	(26)		10	(23)	56
Net loss	(1,301)		(227)	(4,152)	(157)
Total comprehensive income (loss)	$ (1,301)		$ (227)	$ (4,152)	$ (157)