Acquired Sales Contracts (Schedule Of Acquired Sales Contracts) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Net total, assets		$ 6,036.0
Net total, liabilities	88,096.0
Acquired fair value	145,213.0	114,453.0
Accumulated Amortization, Asset	(105,845.0)	(82,376.0)
Total	39,368.0	32,077.0
Acquired fair value	170,341.0	40,654.0
Liability, Accumulated Amortization	(42,877.0)	(14,613.0)
Total	127,464.0	26,041.0
Current Asset [Member]
Coal supply agreement asset	23,474.0	25,063.0
Other Assets [Member]
Coal supply agreement asset	15,894.0	7,014.0
Accrued Expenses And Other Current Liabilities [Member]
Coal Supply Agreement Obligation Liability	58,049.0	5,615.0
Other Noncurrent Liabilities [Member]
Coal Supply Agreement Obligation Liability	$ 69,415.0	$ 20,426.0