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								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic earnings per share:
Net Income	$ 569	$ 541	$ 579	$ 656	$ 102	$ 533	$ 404	$ 506	$ 2,345	$ 1,545	$ 1,678
Weighted average shares outstanding									258.2	269.5	289.3
Basic earnings per share	$ 2.25	$ 2.11	$ 2.22	$ 2.49	$ 0.39	$ 1.99	$ 1.49	$ 1.85	$ 9.08	$ 5.73	$ 5.80
Diluted earnings per share:
Net Income	$ 569	$ 541	$ 579	$ 656	$ 102	$ 533	$ 404	$ 506	$ 2,345	$ 1,545	$ 1,678
Weighted average shares outstanding									258.2	269.5	289.3
Additional shares from assumed issuance of shares under stock-based compensation awards									1.2	1.9	2.1
Weighted average shares and potential shares assumed outstanding for computing diluted earnings per share									259.4	271.4	291.4
Diluted earnings per share	$ 2.24	$ 2.10	$ 2.21	$ 2.48	$ 0.38	$ 1.98	$ 1.48	$ 1.83	$ 9.04	$ 5.69	$ 5.76