Acquired Sales Contracts (Schedule Of Acquired Sales Contracts) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Coal supply agreement asset	$ 60,118	$ 32,077
Coal supply agreement obligation liability	(139,198)	(26,041)
Net total	(79,080)	6,036
Current Asset [Member]
Coal supply agreement asset	35,496	25,063
Other Assets [Member]
Coal supply agreement asset	24,622	7,014
Accrued Expenses And Other Current Liabilities [Member]
Coal supply agreement obligation liability	(80,411)	(5,615)
Other Noncurrent Liabilities [Member]
Coal supply agreement obligation liability	$ (58,787)	$ (20,426)