Debt and Financing Costs (Details Textuals) (USD $)	1 Months Ended		6 Months Ended
	May 31, 2013	Aug. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Short-term Debt [Line Items]
Period For Borrowing Funds			270 days
Line of Credit Facility [Line Items]
Borrowed on uncommitted overdraft lines			$ 48,000,000	$ 46,000,000
Line of Credit Facility, Remaining Borrowing Capacity			2,700,000,000
Line of credit facility, expiration date			P5Y
Debt and Financing Costs (Textuals) [Abstract]
Maturing date of credit facilities	May 31, 2013	Aug. 31, 2011
Carrying Amount, Commercial paper			620,000,000	913,000,000
Period For Borrowing Funds			270 days
Short-term debt, terms			6.25 percent notes due within the next 12 months
Commercial Paper Program Maximum Amount [Member]
Short-term Debt [Line Items]
Commercial paper program			2,950,000,000
Notes Payable, Other Payables [Member]
Short-term Debt [Line Items]
Short term debt borrowings			400,000,000
Unsecured Committed Bank Credit Facilities [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility available to Company	2,300,000,000	1,000,000,000	3,300,000,000
Revolving bank facility			1,500,000,000
Unsecured Committed Bank Credit Facilities in U.S. [Member]
Line of Credit Facility [Line Items]
Revolving bank facility			450,000,000
Unsecured Committed Bank Credit Facilities in Australia [Member]
Line of Credit Facility [Line Items]
Revolving bank facility			200,000,000
Unsecured Committed Bank Credit Facilities in Canada [Member]
Line of Credit Facility [Line Items]
Revolving bank facility			$ 150,000,000
364 Day Facility [Member]
Line of Credit Facility [Line Items]
Period of Revolving bank facility			364 days