Debt and Financing Cost - Additional Information (Detail) (USD $)						3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 United States [Member]	Mar. 31, 2014 Australia [Member]	Mar. 31, 2014 Canada [Member]	Mar. 31, 2014 Notes Payable, Other Payables [Member]	Mar. 31, 2014 Revolving Credit Facility Due August 2016 [Member]	Mar. 31, 2014 Revolving Credit Facility Due June 2017 [Member]
Debt Instrument [Line Items]
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	3,300,000,000
Commercial paper program	3,000,000,000
Period For Borrowing Funds						270 days
Carrying Amount, Commercial paper	0	0
Current debt		$ 53,000,000