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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Basic earnings per share:
Net Income	$ 594	$ 541	$ 1,542	$ 1,776
Weighted average shares outstanding	240.2	256.0	244.8	259.9
Basic earnings per share	$ 2.47	$ 2.11	$ 6.30	$ 6.83
Diluted earnings per share:
Net Income	$ 594	$ 541	$ 1,542	$ 1,776
Weighted average shares outstanding	240.2	256.0	244.8	259.9
Additional shares from assumed issuance of shares under stock-based compensation awards	0.4	1.1	0.6	1.2
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	240.6	257.1	245.4	261.1
Diluted earnings per share	$ 2.47	$ 2.10	$ 6.28	$ 6.80