Debt and Financing Cost - Additional Information (Detail) (USD $)	9 Months Ended				9 Months Ended			9 Months Ended				3 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Commercial Paper [Member]	Sep. 30, 2013 Notes Payable, Other Payables [Member]	Sep. 30, 2013 Australia [Member]	Sep. 30, 2013 Canada [Member]	Sep. 30, 2013 6.00 - Percent Notes [Member]	Sep. 30, 2013 5.25 - Percent Notes [Member]	Sep. 30, 2013 Uncommitted Credit Lines [Member]	Dec. 31, 2012 Uncommitted Credit Lines [Member]	Sep. 30, 2013 Revolving Credit Facility Due August Two Thousand Sixteen [Member]	Sep. 30, 2013 Revolving Credit Facility Due June Two Thousand Seventeen [Member]	Sep. 30, 2013 Credit Facility One [Member] United States [Member]	Sep. 30, 2013 Credit Facility Two [Member] United States [Member]
Debt Instrument [Line Items]
Payments on fixed rate debt	$ 900,000,000	$ 400,000,000						$ 400,000,000	$ 500,000,000
Principal amount of senior unsecured, percentage								6.00%	5.25%
Credit facility maturity date								Sep. 15, 2013	Apr. 15, 2013			Aug. 31, 2016	Jun. 30, 2017
Commercial paper program				3,000,000,000
Period For Borrowing Funds					270 days
Carrying Amount, Commercial paper			489,000,000
Unsecured credit facility available to Company	3,300,000,000											1,000,000,000	2,300,000,000
Revolving bank facility						300,000,000	300,000,000							1,700,000,000	1,000,000,000
Line of credit facility, remaining borrowing capacity	3,300,000,000
Uncommitted credit lines , Carrying Amount	$ 57,000,000		$ 91,000,000							$ 57,000,000	$ 91,000,000