Debt and Financing Cost - Additional Information (Detail) (USD $)	6 Months Ended				3 Months Ended							6 Months Ended	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 6.00 - Percent Notes [Member]	Jun. 30, 2013 5.25 - Percent Notes [Member]	Jun. 30, 2013 Uncommitted Credit Lines [Member]	Dec. 31, 2012 Uncommitted Credit Lines [Member]	Jun. 30, 2013 United States [Member]	Jun. 30, 2013 Australia [Member]	Jun. 30, 2013 Canada [Member]	Jun. 30, 2013 Commercial Paper [Member]	Jun. 30, 2013 Notes Payable, Other Payables [Member]	Jun. 30, 2013 Revolving Credit Facility Due August Two Thousand Sixteen [Member]	Jun. 30, 2013 Revolving Credit Facility Due June Two Thousand Seventeen [Member]
Debt Instrument [Line Items]
Current debt	$ 478,000,000		$ 990,000,000	$ 400,000,000
Payments on fixed rate debt	500,000,000	400,000,000			500,000,000
Principal amount of senior unsecured, percentage				6.00%	5.25%
Uncommitted credit lines , Carrying Amount	78,000,000		91,000,000			78,000,000	91,000,000
Unsecured credit facility available to Company	3,300,000,000												1,000,000,000	2,300,000,000
Credit facility maturity date													Aug. 31, 2016	Jun. 30, 2017
Revolving bank facility	1,700,000,000							1,000,000,000	300,000,000	300,000,000
Line of credit facility, remaining borrowing capacity	1,900,000,000
Commercial paper program											3,000,000,000
Period For Borrowing Funds												270 days
Carrying Amount, Commercial paper	$ 1,430,000,000		$ 489,000,000