Earnings Per Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share [Line Items]
Net income	$ 328	$ 594	$ 1,301	$ 844
Weighted-average shares outstanding	339,766,067	338,920,580	339,164,449	338,021,487
Share-based compensation plans	2,907,971	2,768,388	3,006,950	2,596,909
Adjusted weighted-average shares outstanding and assumed conversions	342,674,038	341,688,968	342,171,399	340,618,396
Basic earnings per share	$ 0.96	$ 1.75	$ 3.83	$ 2.50
Diluted earnings per share	$ 0.96	$ 1.74	$ 3.80	$ 2.48
Anti-dilutive share conversions	1,471,035	1,212	1,051,182	81,718