Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011
Reconciliation of unrecognized tax benefits, including related interest and penalties
Unrecognized Tax Benefits, Beginning Balance	$ 71	$ 65
Unrecognized Tax Benefits And Income Tax Penalties And Interest Accrued, Beginning balance	94	86
Unrecognized Tax Benefits, Interest and Penalties Recognized in Income tax expense, Beginning balance	23	21	20
Unrecognized Tax Benefits, Additions Resulting from Current Period Tax Positions	6	6
Unrecognized Tax Benefits, Reductions Resulting from Current Period Tax Positions	(1)
Unrecognized Tax Benefits, Additions Resulting from Prior Period Tax Positions	6	18
Unrecognized Tax Benefits, Reductions Resulting from Prior Period Tax Positions	(1)	(5)
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(4)	(3)
Interest and Penalties Decrease Resulting from Settlements with Tax Authorities	(2)	(1)
Unrecognized Tax Benefits And Income Tax Penalties And Interest Accrued Decrease Resulting From Settlements With Tax Authorities	(6)	(4)
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations	(16)	(10)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	(1)	3
Unrecognized Tax Benefits, Ending Balance	61	71
Unrecognized Tax Benefits And Income Tax Penalties And Interest Accrued, Ending balance	$ 81	$ 94