Debt (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Long-term Debt
Other indebtedness	$ 35,000,000		$ 35,000,000		$ 19,000,000
Long-term debt	4,123,000,000		4,123,000,000		4,106,000,000
Short-term Debt
Other indebtedness	8,000,000		8,000,000		13,000,000
Total short-term debt	408,000,000		408,000,000		413,000,000
Total debt	4,531,000,000		4,531,000,000		4,519,000,000
Other Indebtedness
Total present value of future minimum capital lease payments	7,000,000		7,000,000
Capital lease obligation, interest included in payments	1,000,000		1,000,000
Commercial Paper [Member]
Commercial Paper
Commercial paper program amount	2,000,000,000		2,000,000,000
Maximum days to maturity of debt instruments			397 days
Commercial Paper [Member] | Notes 2013 [Member]
Long-term Debt
Coupon Rate	0.875%		0.875%
Effective Interest Rate	1.078%		1.078%		1.078%
Short-term Debt
Short-term debt	400,000,000		400,000,000		400,000,000
Line of Credit [Member]
Credit Agreement [Abstract]
Maximum borrowing capacity	3,000,000,000		3,000,000,000
Capacity reserved	2,000,000,000		2,000,000,000
Remaining borrowing capacity	1,000,000,000		1,000,000,000
Amount outstanding	0		0
Letters of credit outstanding	0		0
Unsecured Debt [Member]
Long-term Debt
Long-term debt	4,088,000,000		4,088,000,000		4,087,000,000
Senior Notes
Interest expense	26,000,000	21,000,000	79,000,000	37,000,000
Estimated fair value of notes included in long-term debt	4,000,000,000		4,000,000,000
Unsecured Debt [Member] | Notes 2015 - October [Member]
Long-term Debt
Coupon Rate	1.625%		1.625%
Long-term debt	599,000,000		599,000,000		599,000,000
Effective Interest Rate	1.805%		1.805%		1.805%
Unsecured Debt [Member] | Notes 2015 - July [Member]
Long-term Debt
Coupon Rate	0.70%		0.70%
Long-term debt	250,000,000		250,000,000		250,000,000
Effective Interest Rate	0.82%		0.82%		0.82%
Unsecured Debt [Member] | Notes 2017 [Member]
Long-term Debt
Coupon Rate	1.35%		1.35%
Long-term debt	999,000,000		999,000,000		999,000,000
Effective Interest Rate	1.456%		1.456%		1.456%
Unsecured Debt [Member] | Notes 2020 - October [Member]
Long-term Debt
Coupon Rate	3.25%		3.25%
Long-term debt	498,000,000		498,000,000		498,000,000
Effective Interest Rate	3.389%		3.389%		3.389%
Unsecured Debt [Member] | Notes 2022 [Member]
Long-term Debt
Coupon Rate	2.60%		2.60%
Long-term debt	999,000,000		999,000,000		999,000,000
Effective Interest Rate	2.678%		2.678%		2.678%
Unsecured Debt [Member] | Notes 2042 [Member]
Long-term Debt
Coupon Rate	4.00%		4.00%
Long-term debt	$ 743,000,000		$ 743,000,000		$ 742,000,000
Effective Interest Rate	4.114%		4.114%		4.114%
Overdraft Facilities [Member]
Other Indebtedness
Interest rate, minimum			8.00%
Interest rate, maximum			11.00%
Capital Lease Obligations [Member]
Other Indebtedness
Interest rate, minimum			3.00%
Interest rate, maximum			7.00%
Mortgages [Member]
Long-term Debt
Coupon Rate	6.30%		6.30%