Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic earnings per share:
Net Income	$ 579	$ 404	$ 1,235	$ 910
Weighted average shares outstanding	260.5	271.5	261.9	272.9
Basic earnings per share	$ 2.22	$ 1.49	$ 4.72	$ 3.33
Diluted earnings per share:
Net Income	$ 579	$ 404	$ 1,235	$ 910
Weighted average shares outstanding	260.5	271.5	261.9	272.9
Additional shares from assumed issuance of shares under stock-based compensation awards	1.0	1.8	1.3	1.9
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	261.5	273.3	263.2	274.8
Diluted earnings per share	$ 2.21	$ 1.48	$ 4.69	$ 3.31