Calculation of Diluted Shares (Detail) In Millions, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Schedule of Weighted Average Number of Diluted Shares Outstanding [Line Items]
Shares used in computation of basic earnings per share	455	[1]	454	[1]	453	[1]	451	[1]	454	[1]	452	[1]	451	[1]	453	[1]	453	453		447
Total dilutive effect of outstanding stock awards																		8	[2]	9	[2]
Shares used in computation of diluted earnings per share	462	[1]	461	[1]	460	[1]	459	[1]	461	[1]	452	[1]	458	[1]	460	[1]	453	461		456

[1] The sum of quarterly amounts, including per share amounts, may not equal amounts reported for year-to-date periods. This is due to the effects of rounding and changes in the number of weighted-average shares outstanding for each period.

[2] Calculated using the treasury stock method, which assumes proceeds are used to reduce the dilutive effect of outstanding stock awards. Assumed proceeds include the unrecognized deferred compensation of stock awards, and assumed tax proceeds from excess stock-based compensation deductions.