Capital Stock Dividends and Share Repurchases - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 Dividend Declared [Member]	Dec. 31, 2013 Share Repurchase Program [Member]
Stock Repurchase Program [Line Items]
Common stock shares authorized	1,500,000,000	1,500,000,000	1,500,000,000
Common stock par value per share	$ 0.01	$ 0.01	$ 0.01
Common stock shares issued	630,282,461	630,282,461	630,282,461
Common stock shares outstanding	464,200,000	464,200,000	460,500,000	475,000,000
Preferred stock shares authorized	10,000,000	10,000,000
Preferred stock par value per share	$ 0.01	$ 0.01
Preferred stock shares outstanding	0	0
Cash dividends		$ 658	$ 637	$ 604
Cash dividends declared per common share	$ 0.355	$ 1.42	$ 1.36	$ 1.26
Expected quarterly common stock dividend per share declared					$ 0.365
Maximum capital allocated for repurchases of common stock		$ 500				$ 500