Debt (Details) (USD $)	9 Months Ended			9 Months Ended					9 Months Ended		9 Months Ended		9 Months Ended		1 Months Ended		9 Months Ended				9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2011 Credit Agreement expiring October 2016 [Member]	Sep. 30, 2012 Credit Agreement expiring October 2016 [Member] Commercial Paper [Member]	Sep. 30, 2012 Uncommitted lines of credit [Member]	Dec. 31, 2011 Uncommitted lines of credit [Member]	Sep. 30, 2012 5.90% Senior Notes due April 15, 2016 [Member]	Dec. 31, 2011 5.90% Senior Notes due April 15, 2016 [Member]	Sep. 30, 2012 6.25% Senior Notes due July 15, 2019 [Member]	Dec. 31, 2011 6.25% Senior Notes due July 15, 2019 [Member]	Sep. 30, 2012 4.45% Senior Notes due August 15, 2020 [Member]	Dec. 31, 2011 4.45% Senior Notes due August 15, 2020 [Member]	Aug. 31, 2012 3.625% Senior Notes due May 1, 2022 [Member]	Apr. 30, 2012 3.625% Senior Notes due May 1, 2022 [Member]	Sep. 30, 2012 3.625% Senior Notes due May 1, 2022 [Member]	Dec. 31, 2011 3.625% Senior Notes due May 1, 2022 [Member]	Sep. 30, 2012 Other notes and loans [Member]	Dec. 31, 2011 Other notes and loans [Member]	Sep. 30, 2012 Convertible Notes - due July 31, 2032 [Member]	Dec. 31, 2011 Convertible Notes - due July 31, 2032 [Member]	Sep. 30, 2012 Convertible Notes - due June 15, 2033 [Member]	Dec. 31, 2011 Convertible Notes - due June 15, 2033 [Member]	Sep. 30, 2012 Convertible Notes - due July 1, 2038 [Member]	Dec. 31, 2011 Convertible Notes - due July 1, 2038 [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity				$ 2,500,000,000		$ 1,500,000,000
Credit Agreement, expiration date				Oct. 12, 2016
Available and unused lines of credit	3,378,200,000		3,258,300,000	2,500,000,000	2,500,000,000		878,200,000	758,300,000
Short-Term Borrowings [Abstract]
Short-term borrowings	11,100,000		9,500,000
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	3,750,400,000		2,501,300,000						1,000,000,000	1,000,000,000	500,000,000	500,000,000	1,000,000,000	1,000,000,000			1,250,000,000	0	400,000	1,300,000
Long-term notes payable, Unamortized premium (discount) on Senior Notes, net	16,200,000		(7,600,000)
Long-term notes payable, deferred gain from termination of interest rate swaps on Senior Notes due 2016	25,000,000		30,500,000
Long-term notes payable, total	3,791,600,000		2,524,200,000
Long-term notes payable, current portion	400,000		700,000
Long-Term Notes Payable	3,791,200,000		2,523,500,000
Long-term notes payable, issuance date															Aug. 09, 2012	Apr. 23, 2012
Long-term notes payable, issuance of long-term notes payable															500,000,000	750,000,000
Long-term notes payable, issue price															105.287%	99.567%
Long-term notes payable, proceeds from issuance of long-term notes payable	1,273,200,000	300,000															1,273,200,000
Convertible Debt [Abstract]
Convertible debt, total	659,400,000		659,400,000																		252,700,000	252,700,000	100,000	100,000	406,600,000	406,600,000
Convertible debt, current	0		0
Convertible Debt	$ 659,400,000		$ 659,400,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate									5.90%		6.25%		4.45%				3.625%				0.00%		0.00%		0.00%
Maturity date									Apr. 15, 2016		Jul. 15, 2019		Aug. 15, 2020				May 01, 2022				Jul. 31, 2032		Jun. 15, 2033		Jul. 01, 2038