Income Taxes (Legislative Changes Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended			3 Months Ended
	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Previous [Member]	Dec. 31, 2010 Subsequent [Member]
Mexico IETU Tax Rate Percentage			17.50%	17.00%
Mexico IETU Tax Expense (Benefit)		$ 4	$ 19	$ (5)
Tax liability				73
Increase (Decrease) In Accrued Taxes Payable Due To Application of MTRs			(70)
2010 Tax Relief Act reduction to income taxes payable		$ 27
2010 Tax Relief Act bonus depreciation for qualified investments					50.00%	100.00%
2010 Tax Relief Act bonus depreciation for qualified property	50.00%