Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic earnings per share:
Net Income	$ 494	$ 499	$ 869	$ 948
Weighted average shares outstanding	230.6	245.7	232.0	247.1
Basic earnings per share	$ 2.14	$ 2.03	$ 3.75	$ 3.84
Diluted earnings per share:
Net Income	$ 494	$ 499	$ 869	$ 948
Weighted average shares outstanding	230.6	245.7	232.0	247.1
Additional shares from assumed issuance of shares under stock-based compensation awards	0.4	0.5	0.6	0.6
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	231.0	246.2	232.6	247.7
Diluted earnings per share	$ 2.14	$ 2.03	$ 3.74	$ 3.83