Dispositions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Ownership Interest in Joint Venture Surface Mines	Dec. 31, 2010 Ownership Interest in Joint Venture Surface Mines	Dec. 31, 2009 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					60	67
Cost of Revenue					56	66
Selling, General, and Administrative Costs					0	1
Depreciation and Amortization					6	9
Total Operating Expenses					62	76
Operating Loss					(2)	(9)
Other Income					1	15
Income (Loss) From Discontinued Operations	$ 71	$ (1)	$ 6		$ (1)	$ 6