Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010	Nov. 30, 2010
Summary of debt
Total	$ 700	$ 700	$ 700
Unaccreted Discount	(2)	(3)
Total	698	697
1.500% Fixed Rate Notes Due 2013 [Member]
Summary of debt
Total			300
Effective Rate	1.605%	1.605%
Total	300	300
2.375% Fixed Rate Notes Due 2015 [Member]
Summary of debt
Total			400
Effective Rate	2.494%	2.494%
Total	$ 400	$ 400