Long-Term Debt and Common Stock (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Debt Instrument Table [Line Items]
Total Long-Term Debt	$ 5,260,000,000		$ 5,260,000,000		$ 5,260,000,000
Current Portion of Long-Term Debt	220,000,000		220,000,000		220,000,000
Total Long-Term Debt, Net	5,007,746,000		5,007,746,000		5,003,341,000
Line of Credit Facility [Line Items]
Average Commercial Paper Borrowings Outstanding			2,000,000
Weighted average interest rate			0.32%
Maximum total debt-to-total capitalization ratio allowed under financial covenant (in hundredths)	65.00%		65.00%
Fair Value Of Debt [Abstract]
Fair Value of Debt	5,816,000,000		5,816,000,000		5,602,000,000
Common Stock [Abstract]
Common Stock Dividends Declared	$ 0.160	$ 0.155	$ 0.480	$ 0.465
Common Stock Sold			1,388,270,000	0
Common Stock, Par (in dollars per share)	$ 0.01		$ 0.01		$ 0.01
Shares of Common Stock Sold			13,570,000
Public Offering Price of Common Stock Sold (per share)			$ 105.50
Revolving Credit Agreement 2005 [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	1,000,000,000		1,000,000,000
Eurodollar rate at period end (in hundredths)	0.43%		0.43%
Base rate at period end (in hundredths)	3.25%		3.25%
Revolving Credit Agreement 2010 [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	1,000,000,000		1,000,000,000
Eurodollar rate at period end (in hundredths)	1.81%		1.81%
Base rate at period end (in hundredths)	3.83%		3.83%
Revolving Credit Agreement New Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	2,000,000,000		2,000,000,000
Maximum capacity which may be requested by borrower	$ 3,000,000,000		$ 3,000,000,000