Supplemental Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 420,298		$ 644,462	$ 848,404	$ 1,321,467
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	419,042		566,252	838,358	1,128,574
Depreciation, depletion and amortization	58,459		97,372	122,158	202,246
Amortization of acquired sales contracts, net	1		(1,644)	(832)	(5,034)
Change in fair value of coal derivatives and coal trading activities, net	1,158		1,211	2,368	2,431
Asset impairment and mine closure costs	43,701	$ 85,500	19,146	129,221	19,146
Selling, general and administrative expenses	19,019		24,268	38,845	46,873
Other operating (income) expense, net	(10,561)		7,403	(12,781)	16,489
Total operating expenses	530,819		714,008	1,117,337	1,410,725
Loss from investment in subsidiaries	0		0	0	0
Loss from operations	(110,521)		(69,546)	(268,933)	(89,258)
Interest expense, net
Interest expense (contractual interest of $100,767 and $199,332 for the three and six months ended June 30, 2016)	(45,273)		(99,574)	(89,724)	(198,826)
Interest and investment income	933		962	2,071	3,335
Interest expense, net	(44,340)		(98,612)	(87,653)	(195,491)
Nonoperating expense
Expenses related to proposed debt restructuring	0		(4,016)	(2,213)	(4,016)
Reorganization items, net	(21,271)		0	(25,146)	0
Nonoperating income (expense)	(21,271)		(4,016)	(27,359)	(4,016)
Loss before income taxes	(176,132)		(172,174)	(383,945)	(288,765)
Benefit from income taxes	(245)		(4,071)	(1,356)	(7,467)
Net loss	(175,887)		(168,103)	(382,589)	(281,298)
Total comprehensive income (loss)	(178,294)		(167,887)	(384,136)	(277,478)
Contractual interest	100,767			199,332
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)	(548)		(847)	(1,095)	(1,681)
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
Selling, general and administrative expenses	(343)		(493)	(710)	(1,019)
Other operating (income) expense, net	891		1,340	1,805	2,700
Total operating expenses	0		0	0	0
Loss from investment in subsidiaries	78,965		30,462	202,953	9,413
Loss from operations	78,965		30,462	202,953	9,413
Interest expense, net
Interest expense (contractual interest of $100,767 and $199,332 for the three and six months ended June 30, 2016)	29,772		27,360	60,155	54,202
Interest and investment income	(29,772)		(27,360)	(60,155)	(54,202)
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	78,965		30,462	202,953	9,413
Benefit from income taxes	0		0	0	0
Net loss	78,965		30,462	202,953	9,413
Total comprehensive income (loss)	81,818		30,624	206,808	6,335
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)	3,351		5,908	5,537	13,378
Depreciation, depletion and amortization	738		1,013	1,494	2,073
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	3,101		1,225	6,330	1,225
Selling, general and administrative expenses	12,959		17,166	26,497	32,605
Other operating (income) expense, net	(3,455)		(138)	(4,552)	3,562
Total operating expenses	16,694		25,174	35,306	52,843
Loss from investment in subsidiaries	(78,965)		(30,462)	(202,953)	(9,413)
Loss from operations	(95,659)		(55,636)	(238,259)	(62,256)
Interest expense, net
Interest expense (contractual interest of $100,767 and $199,332 for the three and six months ended June 30, 2016)	(66,126)		(119,231)	(132,365)	(237,286)
Interest and investment income	6,924		6,675	14,034	14,747
Interest expense, net	(59,202)		(112,556)	(118,331)	(222,539)
Nonoperating expense
Expenses related to proposed debt restructuring	0		(4,016)	(2,213)	(4,016)
Reorganization items, net	(21,271)			(25,146)
Nonoperating income (expense)	(21,271)			(27,359)
Loss before income taxes	(176,132)		(172,208)	(383,949)	(288,811)
Benefit from income taxes	(245)		(4,105)	(1,360)	(7,513)
Net loss	(175,887)		(168,103)	(382,589)	(281,298)
Total comprehensive income (loss)	(178,294)		(167,887)	(384,136)	(277,478)
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	420,298		644,462	848,404	1,321,467
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	416,239		561,191	833,916	1,116,877
Depreciation, depletion and amortization	57,721		96,359	120,664	200,171
Amortization of acquired sales contracts, net	1		(1,644)	(832)	(5,034)
Change in fair value of coal derivatives and coal trading activities, net	1,158		1,211	2,368	2,431
Asset impairment and mine closure costs	40,600		17,921	122,891	17,921
Selling, general and administrative expenses	5,268		6,270	10,651	12,514
Other operating (income) expense, net	(7,117)		7,483	(8,268)	12,760
Total operating expenses	513,870		688,791	1,081,390	1,357,640
Loss from investment in subsidiaries	0		0	0	0
Loss from operations	(93,572)		(44,329)	(232,986)	(36,173)
Interest expense, net
Interest expense (contractual interest of $100,767 and $199,332 for the three and six months ended June 30, 2016)	(6,607)		(6,576)	(12,973)	(13,340)
Interest and investment income	22,565		20,256	45,858	40,030
Interest expense, net	15,958		13,680	32,885	26,690
Nonoperating expense
Expenses related to proposed debt restructuring	0			0
Reorganization items, net	0			0
Nonoperating income (expense)	0			0
Loss before income taxes	(77,614)		(30,649)	(200,101)	(9,483)
Benefit from income taxes	0		0	0	0
Net loss	(77,614)		(30,649)	(200,101)	(9,483)
Total comprehensive income (loss)	(80,467)		(30,811)	(203,956)	(6,405)
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
Selling, general and administrative expenses	1,135		1,325	2,407	2,773
Other operating (income) expense, net	(880)		(1,282)	(1,766)	(2,533)
Total operating expenses	255		43	641	242
Loss from investment in subsidiaries	0		0	0	0
Loss from operations	(255)		(43)	(641)	(242)
Interest expense, net
Interest expense (contractual interest of $100,767 and $199,332 for the three and six months ended June 30, 2016)	(2,312)		(1,127)	(4,541)	(2,402)
Interest and investment income	1,216		1,391	2,334	2,760
Interest expense, net	(1,096)		264	(2,207)	358
Nonoperating expense
Expenses related to proposed debt restructuring	0			0
Reorganization items, net	0			0
Nonoperating income (expense)	0			0
Loss before income taxes	(1,351)		221	(2,848)	116
Benefit from income taxes			34	4	46
Net loss	(1,351)		187	(2,852)	70
Total comprehensive income (loss)	$ (1,351)		$ 187	$ (2,852)	$ 70