Income Taxes (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes (Textual) [Abstract]
Tax benefits that, if recognized, would affect the effective tax rate	$ 28	$ 22	$ 18
Recognized expense (benefit) in interest and penalties	2	3	(1)
Accrued interest and penalties related to unrecognized tax benefits	15	14
Expected decrease in gross unrecognized tax benefits in the next twelve months	6
Total income tax expense, computed by applying the statutory U.S. federal income tax rate to income before taxes	$ 620	$ 572	$ 531
U.S. federal income tax rate	35.00%	35.00%	35.00%