Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic earnings per share: [Abstract]
Net Income	$ 404	$ 419	$ 910	$ 928
Weighted average shares outstanding	271.5	293.6	272.9	296.0
Basic earnings per share	$ 1.49	$ 1.43	$ 3.33	$ 3.14
Diluted earnings per share: [Abstract]
Net Income	$ 404	$ 419	$ 910	$ 928
Weighted average shares outstanding	271.5	293.6	272.9	296.0
Additional shares from assumed issuance of shares under stock-based compensation awards	1.8	1.8	1.9	1.7
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	273.3	295.4	274.8	297.7
Diluted earnings per share	$ 1.48	$ 1.42	$ 3.31	$ 3.12