Capital Stock - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended			1 Months Ended	3 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jul. 28, 2010 Series D Preferred Stock [Member]	Jun. 30, 2013 Series D Preferred Stock [Member]	Jun. 30, 2012 Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options and restricted stock, anti-dilutive	6,700,000		4,400,000	7,400,000	3,700,000				14,400,000
Common stock dividend paid	$ 78,000,000		$ 65,000,000	$ 145,000,000	$ 123,000,000
Dividend, Preferred Stock, Cash	19,000,000		19,000,000	38,000,000	38,000,000
Increase in quarterly cash dividend		18.00%
Dividend, Common Stock		$ 0.20
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	2,924,271
Common stock share repurchase, per share	$ 85.47
Preferred stock, shares issued	1,265,000			1,265,000		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	1.625
Maximum common shares issued to convertible preferred stock								14,400,000