Debt Obligations (Interest Expense Recognized On Convertible Senior Notes In The Condensed Consolidated Statements Of Income) (Details) (2.50% Convertible Senior Notes Due August 15, 2013 [Member], USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
2.50% Convertible Senior Notes Due August 15, 2013 [Member]
Debt Instrument [Line Items]
Accretion of debt discount	$ 4	$ 4	$ 11	$ 11
Contractual interest	3	2	8	7
Total interest expense recognized on our 2.50% convertible senior notes	$ 7	$ 6	$ 19	$ 18