Workers' Compensation And Pneumoconiosis (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Workers Compensation And Pneumoconiosis
Beginning balance	$ 70,965,000	$ 66,371,000	$ 67,687,000	$ 63,220,000	$ 63,220,000
Accruals increase	5,557,000	5,005,000	11,114,000	9,811,000
Payments	(2,801,000)	(2,293,000)	(6,028,000)	(4,818,000)
Interest accretion	794,000	833,000	1,587,000	1,666,000
Valuation loss		134,000	155,000	171,000
Ending balance	74,515,000	70,050,000	74,515,000	70,050,000	67,687,000
Increase to black lung obligation					$ 8,300,000