Capital Stock - Additional Information (Detail) (USD $)	3 Months Ended				9 Months Ended			3 Months Ended		9 Months Ended	1 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Convertible Preferred Stock [Member]	Sep. 30, 2012 Convertible Preferred Stock [Member]	Sep. 30, 2012 Convertible Preferred Stock [Member]	Aug. 31, 2013 Series D Preferred Stock [Member]	Jul. 28, 2010 Series D Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options and restricted stock, anti-dilutive	5,400,000			5,100,000	6,000,000	4,100,000		4,800,000	14,300,000	14,300,000
Common stock dividend paid	$ 78,000,000			$ 67,000,000	$ 223,000,000	$ 189,000,000
Dividend, Preferred Stock, Cash					44,000,000	57,000,000
Increase in quarterly cash dividend			18.00%
Dividend, Common Stock			$ 0.2
Common stock share purchase, shares	30,000,000				30,000,000
Common stock share purchase, value					$ 2,000,000,000
Common stock share repurchase, shares	5,043,713	2,924,271
Common stock share repurchase, per share	$ 88.73	$ 85.47
Preferred stock, shares issued							1,265,000					25,300,000
Depository shares each representing												1/20th interest
Mandatory convertibles preferred stock, Series D												6.00%
Preferred stock, shares authorized	10,000,000				10,000,000		10,000,000					1.265
Maximum common shares issued to convertible preferred stock											14,400,000