Stockholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2008
Repurchases of Common Stock, shares authorized to repurchase				250.0
Repurchases of Common Stock		$ 868,065,000
Repurchases of Common Stock, shares	0
Plan to spend for the year on common stock repurchases			700,000,000
Total Repurchases of Common Stock, shares	195.8
Total Repurchases of Common Stock	$ 3,700,000,000
Common stock excluded from calculation of diluted earnings per share	4.6	15.9
Shares authorized for future repurchases	54.2