Segment Information (Schedule Of Operating Segment Results) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 550,305	$ 688,544	$ 1,398,709	$ 2,010,011
Adjusted EBITDAR	81,368	134,805	62,982	261,905
Depreciation, depletion and amortization	69,423	103,965	191,581	306,211
Amortization of acquired sales contracts, net	104	(1,994)	(728)	(7,028)
Capital expenditures	8,296	9,889	82,434	109,250
Operating Segments [Member] | PRB [Member]
Segment Reporting Information [Line Items]
Revenues	295,891	390,360	726,747	1,124,046
Adjusted EBITDAR	73,299	86,204	96,242	214,920
Depreciation, depletion and amortization	37,246	47,321	100,151	134,393
Amortization of acquired sales contracts, net	104	(1,124)	134	(3,170)
Capital expenditures	113	869	612	22,263
Operating Segments [Member] | APP [Member]
Segment Reporting Information [Line Items]
Revenues	190,704	205,573	535,262	653,310
Adjusted EBITDAR	11,616	41,754	13,261	92,988
Depreciation, depletion and amortization	20,749	44,098	62,500	135,028
Amortization of acquired sales contracts, net	0	(870)	(862)	(3,858)
Capital expenditures	7,043	3,990	17,413	15,323
Operating Segments [Member] | Other Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	63,710	92,611	136,700	232,655
Adjusted EBITDAR	20,963	12,927	18,230	22,074
Depreciation, depletion and amortization	10,635	11,193	26,678	32,082
Amortization of acquired sales contracts, net	0	0	0	0
Capital expenditures	1,000	2,889	3,910	7,199
Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Adjusted EBITDAR	(24,510)	(6,080)	(64,751)	(68,077)
Depreciation, depletion and amortization	793	1,353	2,252	4,708
Amortization of acquired sales contracts, net	0	0	0	0
Capital expenditures	$ 140	$ 2,141	$ 60,499	$ 64,465