Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance as of January 1	$ 34	$ 35	$ 47
Tax positions related to the current period, Gross increase
Tax positions related to the current period, Gross decrease
Tax positions related to prior period, Gross increase	2	1	2
Tax positions related to prior period, Gross decrease	(20)	(1)	(10)
Tax positions related to prior period, Settlements	(3)		(3)
Tax positions related to prior period, Lapse of statutes of limitations	(1)	(1)	(1)
Balance as of December 31	$ 12	$ 34	$ 35

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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