Debt (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Lines of Credit [Abstract]
Available and unused lines of credit	$ 3,419,700,000	$ 3,378,200,000
Short-Term Borrowings [Abstract]
Short-term borrowings	11,600,000	6,400,000
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	3,750,400,000	3,750,400,000
Unamortized premium (discount) on Senior Notes, net	15,600,000	16,000,000
Deferred gain from termination of interest rate swaps on Senior Notes due 2016	21,300,000	23,100,000
Long-term notes payable, total	3,787,300,000	3,789,500,000
Long-term notes payable, current portion	400,000	400,000
Long-Term Notes Payable	3,786,900,000	3,789,100,000
Convertible Debt [Abstract]
Convertible debt, total	659,400,000	659,400,000
Convertible debt, current	0	0
Convertible Debt	659,400,000	659,400,000
Credit Agreement expiring October 2016 [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	2,500,000,000
Credit Agreement, expiration date	Oct. 12, 2016
Available and unused lines of credit	2,500,000,000	2,500,000,000
Credit Agreement, covenant terms	The Credit Agreement contains financial covenants that restrict our ability to incur indebtedness as defined in the agreement. These financial covenants limit the Leverage Ratio of total consolidated indebtedness to total consolidated EBITDA to no more than 3 times for the most recently ended 12 month period (under the Credit Agreement, EBITDA is defined as earnings before interest, taxes, depreciation and amortization). We are also required to maintain a minimum Interest Coverage Ratio of consolidated EBITDA to interest expense of at least 5 times for the most recently ended 12 month period.
Credit Agreement, covenant compliance	At March 31, 2013 we were in compliance with these covenants, as our Leverage Ratio was 2.1 times and our Interest Coverage Ratio was 11.0 times.
Credit Agreement expiring October 2016 [Member] | Commercial Paper [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	1,500,000,000
Uncommitted lines of credit [Member]
Lines of Credit [Abstract]
Available and unused lines of credit	919,700,000	878,200,000
5.90% Senior Notes due April 15, 2016
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,000,000,000	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	5.90%
Maturity date	Apr. 15, 2016
6.25% Senior Notes due July 15, 2019
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	500,000,000	500,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	6.25%
Maturity date	Jul. 15, 2019
4.45% Senior Notes due August 15, 2020
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,000,000,000	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	4.45%
Maturity date	Aug. 15, 2020
3.625% Senior Notes due May 1, 2022
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,250,000,000	1,250,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	3.625%
Maturity date	May 01, 2022
Other notes and loans
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	400,000	400,000
Convertible Notes - due July 31, 2032
Convertible Debt [Abstract]
Convertible debt, total	252,700,000	252,700,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	0.00%
Maturity date	Jul. 31, 2032
Convertible Notes - due June 15, 2033
Convertible Debt [Abstract]
Convertible debt, total	100,000	100,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	0.00%
Maturity date	Jun. 15, 2033
Convertible Notes - due July 1, 2038
Convertible Debt [Abstract]
Convertible debt, total	$ 406,600,000	$ 406,600,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	0.00%
Maturity date	Jul. 01, 2038