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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Basic earnings per share:
Net Income	$ 499	$ 579	$ 948	$ 1,235
Weighted average shares outstanding	245.7	260.5	247.1	261.9
Basic earnings per share	$ 2.03	$ 2.22	$ 3.84	$ 4.72
Diluted earnings per share:
Net Income	$ 499	$ 579	$ 948	$ 1,235
Weighted average shares outstanding	245.7	260.5	247.1	261.9
Additional shares from assumed issuance of shares under stock-based compensation awards	0.5	1.0	0.6	1.3
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	246.2	261.5	247.7	263.2
Diluted earnings per share	$ 2.03	$ 2.21	$ 3.83	$ 4.69