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
	Mar. 31, 2014	Mar. 31, 2013
Basic earnings per share:
Net Income	$ 449	$ 656
Weighted average shares outstanding	248.6	263.3
Basic earnings per share	$ 1.81	$ 2.49
Diluted earnings per share:
Net Income	$ 449	$ 656
Weighted average shares outstanding	248.6	263.3
Additional shares from assumed issuance of shares under stock-based compensation awards	0.6	1.5
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share	249.2	264.8
Diluted earnings per share	$ 1.80	$ 2.48