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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic earnings per share:
Net Income	$ 541	$ 533	$ 1,776	$ 1,443
Weighted average shares outstanding	256.0	267.3	259.9	271.0
Basic earnings per share	$ 2.11	$ 1.99	$ 6.83	$ 5.32
Diluted earnings per share:
Net Income	$ 541	$ 533	$ 1,776	$ 1,443
Weighted average shares outstanding	256.0	267.3	259.9	271.0
Additional shares from assumed issuance of shares under stock-based compensation awards	1.1	1.9	1.2	1.9
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	257.1	269.2	261.1	272.9
Diluted earnings per share	$ 2.10	$ 1.98	$ 6.80	$ 5.29