Capital Stock - Net Income Per Common Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Income attributable to common stock	$ 1,016	$ 337	$ 1,714	$ 1,115
Mandatory Convertible Preferred Stock	19		38	38
Income attributable to common stock, including assumed conversions	$ 1,035	$ 337	$ 1,752	$ 1,153
Income attributable to common stock, shares	392	389	392	387
Mandatory Convertible Preferred Stock	14		14	14
Stock options and other	2	1	2	2
Income attributable to common stock, including assumed conversions, shares	408	390	408	403
Income attributable to common stock, per share	$ 2.59	$ 0.87	$ 4.37	$ 2.88
Income attributable to common stock, including assumed conversions, per share	$ 2.54	$ 0.86	$ 4.30	$ 2.86