Significant Financing Transactions - (Commercial Paper, Bank Loans and Letters of Credit Outstanding) (Details) (USD $)	6 Months Ended
	Jun. 30, 2011
Facility Limit	$ 3,500,000,000
Outstanding Commercial Paper	1,786,000,000
Outstanding Letters of Credit	55,000,000
Facility Capacity Available	1,659,000,000
Credit facility, to support letters of credit	1,500,000,000
Credit Facility 1.5 Billion [Member] | Three-Year Joint Revolving Credit Facility [Member]
Facility Limit	3,000,000,000	[1]
Outstanding Commercial Paper	1,786,000,000	[1]
Outstanding Letters of Credit	1,000,000	[1]
Facility Capacity Available	1,213,000,000	[1]
Credit facility initiation date	September 2010
Credit facility termination date	September 2013
Three-Year Joint Revolving Credit Facility [Member]
Facility Limit	500,000,000	[2]
Outstanding Letters of Credit	54,000,000	[2]
Facility Capacity Available	$ 446,000,000	[2]
Credit facility initiation date	September 2010
Credit facility termination date	September 2013

[1] This credit facility was entered into in September 2010 and terminates in September 2013. This credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.5 billion of letters of credit.

[2] This credit facility was entered into in September 2010 and terminates in September 2013. This credit facility can be used to support bank borrowings, commercial paper and letter of credit issuances.