Supplemental Guarantor and Non-Guarantor Financial Information (Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues:
Sales	$ 193,835	$ 377,982	$ 479,481	$ 783,211
Miscellaneous income	2,792	369	8,072	9,025
Total revenues	196,627	378,351	487,553	792,236
Costs and expenses:
Cost of sales (exclusive of depreciation and depletion)	225,867	343,761	510,560	693,636
Depreciation and depletion	51,478	69,816	110,660	146,240
Selling, general and administrative	28,229	19,002	49,290	39,781
Other postretirement benefits	12,333	13,869	24,666	27,738
Restructuring charges	2,446	8,299	2,446	8,299
Asset impairments	2,897,928	23,043	2,897,928	23,043
Total costs and expenses	3,218,281	477,790	3,595,550	938,737
Operating loss	(3,021,654)	(99,439)	(3,107,997)	(146,501)
Interest expense, net	(74,851)	(73,402)	(153,087)	(138,834)
Gain (loss) on extinguishment of debt	0	11,397	58,626	(2,492)
Other income (loss), net	0	978	0	(778)
Loss before income tax benefit	(3,096,505)	(160,466)	(3,202,458)	(288,605)
Income tax expense (benefit)	(641,441)	(9,075)	(667,198)	(45,036)
Equity in net losses of subsidiaries	0	0	0	0
Net loss	(2,455,064)	(151,391)	(2,535,260)	(243,569)
Reportable legal entities | Parent (Issuer)
Revenues:
Sales	0	0	0	0
Miscellaneous income	775	324	1,228	979
Total revenues	775	324	1,228	979
Costs and expenses:
Cost of sales (exclusive of depreciation and depletion)	0	0	0	0
Depreciation and depletion	599	613	1,174	1,261
Selling, general and administrative	14,458	1,961	19,841	3,114
Other postretirement benefits	(66)	(44)	(133)	(88)
Restructuring charges	355	514	355	514
Asset impairments	0	0	0	0
Total costs and expenses	15,346	3,044	21,237	4,801
Operating loss	(14,571)	(2,720)	(20,009)	(3,822)
Interest expense, net	(75,234)	(72,338)	(151,590)	(144,742)
Gain (loss) on extinguishment of debt		11,397	58,626	(2,492)
Other income (loss), net		981		(719)
Loss before income tax benefit	(89,805)	(62,680)	(112,973)	(151,775)
Income tax expense (benefit)	(3,239)	16,128	(3,239)	(2,433)
Equity in net losses of subsidiaries	(2,368,498)	(72,583)	(2,425,526)	(94,227)
Net loss	(2,455,064)	(151,391)	(2,535,260)	(243,569)
Reportable legal entities | Guarantor Subsidiaries
Revenues:
Sales	183,315	298,199	431,685	623,110
Miscellaneous income	2,630	1,851	2,885	3,730
Total revenues	185,945	300,050	434,570	626,840
Costs and expenses:
Cost of sales (exclusive of depreciation and depletion)	203,680	244,186	436,096	498,227
Depreciation and depletion	34,012	36,154	70,276	74,255
Selling, general and administrative	10,998	11,647	23,493	25,505
Other postretirement benefits	12,399	13,913	24,799	27,826
Restructuring charges	1,322	681	1,322	681
Asset impairments	0	23,043	0	23,043
Total costs and expenses	262,411	329,624	555,986	649,537
Operating loss	(76,466)	(29,574)	(121,416)	(22,697)
Interest expense, net	(166)	(251)	(361)	6,983
Gain (loss) on extinguishment of debt		0	0	0
Other income (loss), net		0		0
Loss before income tax benefit	(76,632)	(29,825)	(121,777)	(15,714)
Income tax expense (benefit)	0	(6,988)	0	(4,359)
Equity in net losses of subsidiaries	0	0	0	0
Net loss	(76,632)	(22,837)	(121,777)	(11,355)
Reportable legal entities | Non-Guarantor Subsidiaries
Revenues:
Sales	10,520	79,783	47,796	160,101
Miscellaneous income	(613)	(1,806)	3,959	4,316
Total revenues	9,907	77,977	51,755	164,417
Costs and expenses:
Cost of sales (exclusive of depreciation and depletion)	22,187	99,575	74,464	195,409
Depreciation and depletion	16,867	33,049	39,210	70,724
Selling, general and administrative	2,773	5,394	5,956	11,162
Other postretirement benefits	0	0	0	0
Restructuring charges	769	7,104	769	7,104
Asset impairments	2,897,928	0	2,897,928	0
Total costs and expenses	2,940,524	145,122	3,018,327	284,399
Operating loss	(2,930,617)	(67,145)	(2,966,572)	(119,982)
Interest expense, net	549	(813)	(1,136)	(1,075)
Gain (loss) on extinguishment of debt		0	0	0
Other income (loss), net		(3)		(59)
Loss before income tax benefit	(2,930,068)	(67,961)	(2,967,708)	(121,116)
Income tax expense (benefit)	(638,202)	(18,215)	(663,959)	(38,244)
Equity in net losses of subsidiaries	0	0	0	0
Net loss	(2,291,866)	(49,746)	(2,303,749)	(82,872)
Eliminations
Revenues:
Sales	0	0	0	0
Miscellaneous income	0	0	0	0
Total revenues	0	0	0	0
Costs and expenses:
Cost of sales (exclusive of depreciation and depletion)	0	0	0	0
Depreciation and depletion	0	0	0	0
Selling, general and administrative	0	0	0	0
Other postretirement benefits	0	0	0	0
Restructuring charges	0	0	0	0
Asset impairments	0	0	0	0
Total costs and expenses	0	0	0	0
Operating loss	0	0	0	0
Interest expense, net	0	0	0	0
Gain (loss) on extinguishment of debt		0	0	0
Other income (loss), net		0		0
Loss before income tax benefit	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Equity in net losses of subsidiaries	2,368,498	72,583	2,425,526	94,227
Net loss	$ 2,368,498	$ 72,583	$ 2,425,526	$ 94,227