Capital Stock Dividends and Share Repurchases - Stock Repurchase Programs (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Stock Repurchase Program [Line Items]
Shares repurchased (in thousands)	17,338	14,920
Per share purchase price lower range	$ 28.95	$ 31.56
Per share purchase price upper range	$ 39.57	$ 37.05
Total repurchases (in millions)	$ 575	$ 501