Dispositions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011 Ownership Interest in Joint Venture Surface Mines	Mar. 31, 2011 Ownership Interest in Joint Venture Surface Mines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax			$ 72
Revenue				15
Cost of Revenue				15
Selling, General, and Administrative Costs				0
Depreciation and Amortization				1
Total Operating Expenses				16
Operating Loss				(1)
Other Income				0
Income (Loss) From Discontinued Operations	$ 0	$ (1)		$ (1)