Long-Term Debt and Common Stock (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date			Oct. 11, 2016
Common Stock Dividends Declared	$ 0.17	$ 0.16
Uncommitted Credit Facility [Member]
Line of Credit Facility [Line Items]
Weighted average interest rate (in hundredths)			0.70%
Average Borrowings Outstanding			82,000
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Weighted average interest rate (in hundredths)			0.44%
Average Borrowings Outstanding			240,000,000
Revolving Credit Agreement [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,000,000,000		2,000,000,000
Eurodollar rate at period end (in hundredths)	1.12%		1.12%
Base rate at period end (in hundredths)	3.25%		3.25%