Debt (Details) (USD $)	3 Months Ended	12 Months Ended					12 Months Ended			12 Months Ended					12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended			24 Months Ended	3 Months Ended	12 Months Ended		142 Months Ended			3 Months Ended
	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2004	Aug. 18, 2011 Interest Rate Swaps on 2016 Notes [Member]	Dec. 31, 2013 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2012 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2013 Credit Agreement expiring October 2016 [Member] Commercial Paper [Member]	Dec. 31, 2013 Commercial Paper [Member]	Dec. 31, 2012 Commercial Paper [Member]	Dec. 31, 2011 Commercial Paper [Member]	Dec. 31, 2013 Uncommitted lines of credit [Member]	Dec. 31, 2012 Uncommitted lines of credit [Member]	Dec. 31, 2013 Long-Term Notes Payable [Member]	Dec. 31, 2012 Long-Term Notes Payable [Member]	Dec. 31, 2011 Long-Term Notes Payable [Member]	Dec. 31, 2013 5.90% Senior Notes due April 15, 2016	Dec. 31, 2012 5.90% Senior Notes due April 15, 2016	Dec. 31, 2013 6.25% Senior Notes due July 15, 2019	Dec. 31, 2012 6.25% Senior Notes due July 15, 2019	Dec. 31, 2013 4.45% Senior Notes due August 15, 2020	Dec. 31, 2012 4.45% Senior Notes due August 15, 2020	Dec. 31, 2013 3.625% Senior Notes due May 1, 2022	Dec. 31, 2012 3.625% Senior Notes due May 1, 2022	Dec. 31, 2013 Other notes and loans	Dec. 31, 2012 Other notes and loans	Dec. 31, 2013 Convertible Debt [Member]	Dec. 31, 2012 Convertible Debt [Member]	Dec. 31, 2011 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]	Sep. 30, 2013 Convertible Notes due July 31, 2032	Dec. 31, 2013 Convertible Notes due July 31, 2032 Rate	Dec. 31, 2002 Convertible Notes due July 31, 2032	Dec. 31, 2013 Convertible Notes due July 31, 2032	Dec. 31, 2012 Convertible Notes due July 31, 2032	Dec. 31, 2004 Convertible Notes due July 31, 2032 Y	Jun. 30, 2013 2033 Notes and 2038 Notes [Member] Rate	Dec. 31, 2013 Convertible Notes due June 15, 2033	Dec. 31, 2012 Convertible Notes due June 15, 2033	Dec. 31, 2013 Convertible Notes due July 1, 2038	Dec. 31, 2012 Convertible Notes due July 1, 2038	Dec. 31, 2004 Convertible Notes due July 1, 2038 Y
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		3,551,500,000	3,378,200,000				2,500,000,000	2,500,000,000					1,051,500,000	878,200,000
Credit Agreement, covenant terms							The Credit Agreement contains financial covenants that require us to maintain a Leverage Ratio of consolidated indebtedness to 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) and an 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, 2013 we were in compliance with these covenants, as our Leverage Ratio was 1.9 times and our Interest Coverage Ratio was 10.7 times.
Short-Term Borrowings [Abstract]
Short-term borrowings		5,900,000	6,400,000
Short-term borrowings, weighted average interest rate		5.60%	9.50%
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount		3,750,500,000	3,750,400,000															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	1,250,000,000	500,000	400,000
Unamortized premium (discount) on Senior Notes, net		14,700,000	16,000,000
Deferred gain from termination of interest rate swaps on Senior Notes due 2016		15,900,000	23,100,000			(33,200,000)
Long-term notes payable, total		3,781,100,000	3,789,500,000
Long-term notes payable, current portion		400,000	400,000
Long-Term Notes Payable		3,780,700,000	3,789,100,000
Convertible Debt [Abstract]
Convertible debt, total		252,700,000	659,400,000																														252,700,000		252,700,000	252,700,000			0	100,000	0	406,600,000
Convertible debt, current		0	0
Convertible Debt		252,700,000	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%
Maturity date																		Apr. 15, 2016		Jul. 15, 2019		Aug. 15, 2020		May 01, 2022									Jul. 31, 2032
Convertible debt, call date																																						May 16, 2013
Convertible debt, percentage of principal amount redeemed																																						100.00%
Convertible debt, conversion rate																																	18.313					19.4174
Convertible debt, latest conversion date																																						Jun. 13, 2013
Convertible debt, principle amount settled in cash																																						406,100,000
Convertible debt, shares issued for conversion premium																																						1,499,792
Convertible debt, adjustment to additional paid-in capital	34,500,000
Convertible debt, repurchase date																																						Jun. 17, 2013
Convertible debt, repurchase amount																																						600,000
Convertible debt, issuance																																		900,000,000
Convertible debt, repayments of convertible debt																															1,382,000,000				647,300,000
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 at any time on or after July 31, 2014. There are no events that accelerate the noteholders’ put rights.
Convertible debt, contingent interest																																	Our 2032 Notes accrue contingent interest for the periods August 1, 2013 to January 31, 2014 and February 1, 2014 to July 31, 2014. Contingent interest of $2.81 per $1,000 principal amount was paid on October 31, 2013 and is payable on January 31, 2014, April 30, 2014 and July 31, 2014.
Convertible debt, contingent interest derivative, Interest Expense																																2,800,000
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	0
Components of Interest Expense [Abstract]
Interest expense, debt										1,700,000	1,300,000	2,500,000			174,700,000	156,200,000	125,800,000											5,900,000	6,700,000	10,000,000
Interest expense, fees		6,500,000	6,200,000	7,100,000
Interest expense, other		8,400,000	9,300,000	12,700,000
Interest expense, total		197,200,000	179,700,000	158,100,000
Stated Maturities of Long-Term Notes Payable and Convertible Debt [Abstract]
Stated maturities of long-term notes payable and convertible debt, 2014		400,000
Stated maturities of long-term notes payable and convertible debt, 2015		0
Stated maturities of long-term notes payable and convertible debt, 2016		1,000,100,000
Stated maturities of long-term notes payable and convertible debt, 2017		0
Stated maturities of long-term notes payable and convertible debt, 2018		0
Stated maturities of long-term notes payable and convertible debt, Thereafter		3,002,700,000
Stated maturities of long-term notes payable and convertible debt		$ 4,003,200,000