Debt (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended				1 Months Ended		12 Months Ended		12 Months Ended					12 Months Ended					12 Months Ended		12 Months Ended		1 Months Ended		9 Months Ended	12 Months Ended				12 Months Ended			24 Months Ended	12 Months Ended		130 Months Ended			1 Months Ended		12 Months Ended	115 Months Ended		1 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2004	Aug. 31, 2011 Interest Rate Swaps on 2016 Notes [Member]	Aug. 18, 2011 Interest Rate Swaps on 2016 Notes [Member]	Dec. 31, 2012 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2011 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2012 Commercial Paper [Member]	Dec. 31, 2011 Commercial Paper [Member]	Dec. 31, 2010 Commercial Paper [Member]	Dec. 31, 2012 Uncommitted lines of credit [Member]	Dec. 31, 2011 Uncommitted lines of credit [Member]	Dec. 31, 2012 Long-Term Notes Payable [Member]	Dec. 31, 2011 Long-Term Notes Payable [Member]	Dec. 31, 2010 Long-Term Notes Payable [Member]	Dec. 31, 2012 5.90% Senior Notes due April 15, 2016	Dec. 31, 2011 5.90% Senior Notes due April 15, 2016	Dec. 31, 2012 6.25% Senior Notes due July 15, 2019	Dec. 31, 2011 6.25% Senior Notes due July 15, 2019	Dec. 31, 2012 4.45% Senior Notes due August 15, 2020	Dec. 31, 2011 4.45% Senior Notes due August 15, 2020	Aug. 31, 2012 3.625% Senior Notes due May 1, 2022	Apr. 30, 2012 3.625% Senior Notes due May 1, 2022	Sep. 30, 2012 3.625% Senior Notes due May 1, 2022	Dec. 31, 2012 3.625% Senior Notes due May 1, 2022	Dec. 31, 2011 3.625% Senior Notes due May 1, 2022	Dec. 31, 2012 Other notes and loans	Dec. 31, 2011 Other notes and loans	Dec. 31, 2012 Convertible Debt [Member]	Dec. 31, 2011 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]	Dec. 31, 2012 Convertible Notes - due July 31, 2032	Dec. 31, 2002 Convertible Notes - due July 31, 2032	Dec. 31, 2012 Convertible Notes - due July 31, 2032	Dec. 31, 2011 Convertible Notes - due July 31, 2032	Dec. 31, 2004 Convertible Notes - due July 31, 2032 Y	Jun. 30, 2006 Convertible Notes - due June 15, 2033	Jun. 30, 2003 Convertible Notes - due June 15, 2033	Dec. 31, 2012 Convertible Notes - due June 15, 2033	Dec. 31, 2012 Convertible Notes - due June 15, 2033	Dec. 31, 2011 Convertible Notes - due June 15, 2033	Jun. 30, 2010 Convertible Notes - due July 1, 2038	Dec. 31, 2012 Convertible Notes - due July 1, 2038	Dec. 31, 2011 Convertible Notes - due July 1, 2038	Dec. 31, 2004 Convertible Notes - due July 1, 2038 Y	Dec. 31, 2012 Commercial Paper [Member] Credit Agreement expiring October 2016 [Member]	Dec. 31, 2011 Interest Rate Swap [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
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 December 31, 2012 we were in compliance with these covenants, as our Leverage Ratio was 2.1 times and our Interest Coverage Ratio was 11.6 times.
Short-Term Borrowings [Abstract]
Short-term borrowings	6,400,000	9,500,000
Short-term borrowings, weighted average interest rate	9.50%	5.60%
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
Unamortized premium (discount) on Senior Notes, net	16,000,000	(7,600,000)
Deferred gain from termination of interest rate swaps on Senior Notes due 2016	23,100,000	30,500,000				(33,200,000)
Long-term notes payable, total	3,789,500,000	2,524,200,000
Long-term notes payable, current portion	400,000	700,000
Long-Term Notes Payable	3,789,100,000	2,523,500,000
Long-term debt, issue date																							Aug. 09, 2012	Apr. 23, 2012
Long-term debt, issuance																							500,000,000	750,000,000											900,000,000					600,000,000
Long-term debt, issue price																							105.287%	99.567%
Long-term debt, proceeds from issuance	1,273,200,000	0	990,100,000																						1,273,200,000
Proceeds from discontinuation of interest rate swaps	0	38,800,000	0		38,800,000
Reduction of interest expense from interest rate swaps																																																	12,200,000
Convertible Debt [Abstract]
Convertible debt, total	659,400,000	659,400,000																																252,700,000		252,700,000	252,700,000				100,000	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 debt, issuance																							500,000,000	750,000,000											900,000,000					600,000,000
Convertible debt, repayments of convertible debt																																	1,382,000,000			647,300,000						193,300,000
Convertible debt, number of potential common shares																																		4.6							7.9
Convertible debt, conversion price																																		$ 55.01		$ 55.01					$ 51.50	$ 51.50
Convertible debt, put terms																																		Holders of the 2032 Notes have the right to put the notes back to us for cash on July 31 of each year and we have the right to redeem the notes for cash on July 31, 2013 and 2014. After July 31, 2014, we can redeem the 2032 Notes at any time. There are no events that accelerate the noteholders’ put rights.											Holders of the 2038 Notes have the right to put the notes back to us for cash on June 15, 2013, 2018 and 2023 and on each June 15 annually thereafter through June 15, 2037 and we have a right to redeem the notes for cash on June 17, 2013 and June 15, 2018. After June 15, 2018, we can redeem the 2038 Notes at any time. There are no events that accelerate the noteholders’ put rights.
Convertible debt, contingent cash interest due	0
Convertible debt, indenture amendment																																							In June 2006 substantially all of the 2033 Notes then outstanding were amended to extend the maturity of the notes from June 15, 2033 to July 1, 2038. The amended notes are referred to as our Zero Coupon Zero Yield Convertible Notes due 2038 (“2038 Notes”).					In June 2010, the 2038 Notes were amended whereby substantially all of the holders of the 2038 Notes then outstanding agreed to waive their right to contingent cash interest, if payable, from December 15, 2010 through and including December 15, 2013.
Convertible debt, equity component				47,500,000
Convertible debt, equity component, net of tax				28,500,000
Convertible debt, equity component, amortization period																																						1									1.6
Convertible debt, supplemental interest paid	0	0	25,900,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate																	5.90%		6.25%		4.45%					3.625%								0.00%		0.00%					0.00%	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
Components of Interest Expense [Abstract]
Interest expense, debt									1,300,000	2,500,000	1,800,000			156,200,000	125,800,000	106,700,000														6,700,000	10,000,000	10,500,000
Interest expense, fees	6,200,000	7,100,000	5,700,000
Interest expense, other	9,300,000	12,700,000	10,000,000
Interest expense, total	179,700,000	158,100,000	134,700,000
Stated Maturities of Long-Term Notes Payable and Convertible Debt [Abstract]
Stated maturities of long-term notes payable and convertible debt, 2013	400,000
Stated maturities of long-term notes payable and convertible debt, 2014	0
Stated maturities of long-term notes payable and convertible debt, 2015	0
Stated maturities of long-term notes payable and convertible debt, 2016	1,000,000,000
Stated maturities of long-term notes payable and convertible debt, 2017	0
Stated maturities of long-term notes payable and convertible debt, Thereafter	3,409,400,000
Stated maturities of long-term notes payable and convertible debt,	$ 4,409,800,000