Segment Information (Schedule Of Operating Segment Results) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	$ 1,087,618	$ 1,198,673	$ 3,190,807	$ 3,057,139
Income (loss) from operations	135,960	76,256	(398,943)	273,848
Depreciation, depletion and amortization	126,838	139,547	399,672	320,320
Amortization of acquired sales contacts, net	(4,093)	(12,698)	(22,561)	(5,492)
Mine closure and asset impairment costs	(2,194)		523,568	7,316
Total assets	9,935,854	9,961,657	9,935,854	9,961,657	10,213,959
Capital expenditures	101,895	108,173	303,968	215,899
PRB [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	406,719	394,012	1,130,408	1,178,537
Income (loss) from operations	38,873	38,632	94,163	121,118
Depreciation, depletion and amortization	43,944	42,676	122,298	125,532
Amortization of acquired sales contacts, net	(589)	3,802	(1,374)	15,349
Mine closure and asset impairment costs			0
Total assets	2,234,941	2,240,458	2,234,941	2,240,458
Capital expenditures	5,620	20,937	15,399	39,422
APP [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	436,409	611,403	1,409,776	1,336,581
Income (loss) from operations	88,695	63,350	(388,563)	205,701
Depreciation, depletion and amortization	61,596	73,420	210,789	127,526
Amortization of acquired sales contacts, net	(3,711)	(15,701)	(21,658)	(19,907)
Mine closure and asset impairment costs	(1,801)		524,115	7,316
Total assets	3,846,136	5,241,004	3,846,136	5,241,004
Capital expenditures	77,772	62,121	222,177	108,711
WBIT [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	217,963	168,795	562,074	513,388
Income (loss) from operations	40,828	24,653	85,848	95,217
Depreciation, depletion and amortization	17,881	19,125	54,935	61,753
Amortization of acquired sales contacts, net
Mine closure and asset impairment costs	(50)		129
Total assets	676,057	667,658	676,057	667,658
Capital expenditures	13,510	16,110	42,761	38,003
Other [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	26,527	24,463	88,549	28,633
Income (loss) from operations	(1,298)	(1,487)	(3,757)	(1,412)
Depreciation, depletion and amortization	2,594	3,674	9,704	4,210
Amortization of acquired sales contacts, net	207	(832)	471	(934)
Mine closure and asset impairment costs	(210)		(437)
Total assets	454,118	452,491	454,118	452,491
Capital expenditures	3,640	4,705	8,153	9,078
Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue
Income (loss) from operations	(31,138)	(48,892)	(186,634)	(146,776)
Depreciation, depletion and amortization	823	652	1,946	1,299
Amortization of acquired sales contacts, net		33
Mine closure and asset impairment costs	(133)		(239)
Total assets	2,724,602	1,360,046	2,724,602	1,360,046
Capital expenditures	$ 1,353	$ 4,300	$ 15,478	$ 20,685