Segment Information (Schedule Of Operating Segment Results) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Revenues	$ 713,776	$ 766,332	$ 1,449,747	$ 1,503,702
Income (loss) from operations	(35,805)	(36,279)	(108,927)	(87,710)
Depreciation, depletion and amortization	102,464	111,085	206,887	221,278
Amortization of acquired sales contracts, net	(3,239)	(2,209)	(6,935)	(5,019)
Capital expenditures	81,292	114,542	95,746	169,064
PRB [Member]
Segment Reporting Information [Line Items]
Revenues	358,265	353,425	716,872	715,371
Income (loss) from operations	5,103	16,755	204	32,272
Depreciation, depletion and amortization	41,036	42,147	80,281	84,374
Amortization of acquired sales contracts, net	(785)	(941)	(1,574)	(2,140)
Capital expenditures	6,962	1,819	9,056	3,976
APP [Member]
Segment Reporting Information [Line Items]
Revenues	280,961	337,678	560,098	620,296
Income (loss) from operations	(18,274)	(5,220)	(44,002)	(32,336)
Depreciation, depletion and amortization	51,232	56,006	106,220	111,337
Amortization of acquired sales contracts, net	(2,477)	(2,812)	(5,451)	(5,284)
Capital expenditures	11,037	43,470	19,193	92,767
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	74,550	75,229	172,777	168,035
Income (loss) from operations	14,955	12,924	16,728	20,308
Depreciation, depletion and amortization	9,583	11,057	19,102	22,361
Amortization of acquired sales contracts, net	23	1,544	90	2,405
Capital expenditures	2,358	4,771	4,159	5,266
Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues
Income (loss) from operations	(37,589)	(60,738)	(81,857)	(107,954)
Depreciation, depletion and amortization	613	1,875	1,284	3,206
Amortization of acquired sales contracts, net	0	0	0	0
Capital expenditures	$ 60,935	$ 64,482	$ 63,338	$ 67,055