Debt and Credit Facilities (Narrative) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Feb. 15, 2013	Dec. 31, 2012
Commercial Paper	$ 0		$ 0
Short-term borrowings and current maturities of long-term debt	373,200,000		963,700,000
Line of credit facility, amount outstanding	2,000,000,000
Four Year Revolving Credit Facility [Member]
Line of credit facility, amount outstanding	1,000,000,000
Line of credit facility, expiration date	May 20, 2015
Five Year Revolving Credit Facility [Member]
Line of credit facility, amount outstanding	1,000,000,000
Line of credit facility, expiration date	Mar. 15, 2017
Debentures With Put Feature [Member]
Short-term borrowings and current maturities of long-term debt	343,000,000		343,000,000
Debt instrument, maturity date range, start	Jan. 01, 2027
Debt instrument, maturity date range, end	Dec. 31, 2028
Debentures with put option available to be exercised		37,200,000
6.000% Senior Notes Due 2013 [Member]
Short-term borrowings and current maturities of long-term debt	0		600,000,000
Debt Instrument, face amount	600,000,000
Debt instrument, interest rate, stated percentage	6.00%
Senior Notes Issued in 2013 [Member]
Debt Instrument, face amount	1,550,000,000
2.875% Senior notes due 2019 [Member]
Debt Instrument, face amount	350,000,000
Debt instrument, interest rate, stated percentage	2.875%
4.25% Senior notes due 2023 [Member]
Debt Instrument, face amount	700,000,000
Debt instrument, interest rate, stated percentage	4.25%
5.75% Senior notes due 2043 [Member]
Debt Instrument, face amount	500,000,000
Debt instrument, interest rate, stated percentage	5.75%
9.500% Senior Notes Due 2014 [Member]
Debt Instrument, face amount	655,000,000
Debt instrument, interest rate, stated percentage	9.50%
Gains (Losses) on Extinguishment of Debt	$ 45,600,000