Indebtedness Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Short-term borrowings, carrying value	$ 4,085,000,000		$ 1,511,000,000
Long-term debt proceeds	1,220,000,000	0
Revolving Credit Facilities [Member]
Committed credit facilities, maximum borrowing capacity	6,000,000,000
Credit facilities, outstanding amount	0
4.500% U S Dollar Notes Due On March 2042 [Member]
Debt Instrument, Face Amount	700,000,000
Debt instrument interest rate	4.50%
Debt instrument, maturity date	Mar. 01, 2042
1.625% U.S. Dollar Notes Due March 2017 [Member]
Debt Instrument, Face Amount	$ 550,000,000
Debt instrument interest rate	1.625%
Debt instrument, maturity date	Mar. 01, 2017