Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic earnings per share:
Net Income	$ 601	$ 594	$ 1,470	$ 1,542
Weighted average shares outstanding	229.4	240.2	231.2	244.8
Basic earnings per share	$ 2.62	$ 2.47	$ 6.36	$ 6.30
Diluted earnings per share:
Net Income	$ 601	$ 594	$ 1,470	$ 1,542
Weighted average shares outstanding	229.4	240.2	231.2	244.8
Additional shares from assumed issuance of shares under stock-based compensation awards	1.7	0.4	0.9	0.6
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	231.1	240.6	232.1	245.4
Diluted earnings per share	$ 2.60	$ 2.47	$ 6.33	$ 6.28