Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Basic earnings per share [Abstract]
Net Income	$ 452	$ 298	$ 419	$ 509	$ 620	$ 572	$ 518	$ 464	$ 1,678	$ 2,174	$ 2,183
Weighted average shares outstanding									289.3	319.2	350.1
Basic earnings per share	$ 1.62	$ 1.04	$ 1.43	$ 1.71	$ 2.03	$ 1.82	$ 1.60	$ 1.39	$ 5.80	$ 6.81	$ 6.24
Diluted earnings per share [Abstract]
Net Income	$ 452	$ 298	$ 419	$ 509	$ 620	$ 572	$ 518	$ 464	$ 1,678	$ 2,174	$ 2,183
Weighted average shares outstanding									289.3	319.2	350.1
Additional shares from assumed issuance of shares under stock-based compensation awards									2.1	2.4	2.9
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share									291.4	321.6	353.0
Diluted earnings per share	$ 1.6	$ 1.04	$ 1.42	$ 1.70	$ 2.02	$ 1.80	$ 1.59	$ 1.39	$ 5.76	$ 6.76	$ 6.18