Debt (Details) (USD $)	3 Months Ended			9 Months Ended					9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended				0 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended
	Jun. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Credit Agreement expiring October 2016 [Member]	Dec. 31, 2012 Credit Agreement expiring October 2016 [Member]	Sep. 30, 2013 Credit Agreement expiring October 2016 [Member] Commercial Paper [Member]	Sep. 30, 2013 Uncommitted lines of credit [Member]	Dec. 31, 2012 Uncommitted lines of credit [Member]	Sep. 30, 2013 5.90% Senior Notes due April 15, 2016	Dec. 31, 2012 5.90% Senior Notes due April 15, 2016	Sep. 30, 2013 6.25% Senior Notes due July 15, 2019	Dec. 31, 2012 6.25% Senior Notes due July 15, 2019	Sep. 30, 2013 4.45% Senior Notes due August 15, 2020	Dec. 31, 2012 4.45% Senior Notes due August 15, 2020	Sep. 30, 2013 3.625% Senior Notes due May 1, 2022	Dec. 31, 2012 3.625% Senior Notes due May 1, 2022	Sep. 30, 2013 Other notes and loans	Dec. 31, 2012 Other notes and loans	Sep. 24, 2013 Convertible Notes due July 31, 2032 Rate	Sep. 23, 2013 Convertible Notes due July 31, 2032 Rate	Sep. 30, 2013 Convertible Notes due July 31, 2032	Sep. 30, 2013 Convertible Notes due July 31, 2032	Dec. 31, 2012 Convertible Notes due July 31, 2032	Jun. 30, 2013 2033 Notes and 2038 Notes [Member] Rate	Sep. 30, 2013 Convertible Notes due June 15, 2033	Dec. 31, 2012 Convertible Notes due June 15, 2033	Sep. 30, 2013 Convertible Notes due July 1, 2038	Dec. 31, 2012 Convertible Notes due July 1, 2038
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		3,583,400,000	3,378,200,000	2,500,000,000	2,500,000,000		1,083,400,000	878,200,000
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 September 30, 2013 we were in compliance with these covenants, as our Leverage Ratio was 1.9 times and our Interest Coverage Ratio was 10.6 times.
Short-Term Borrowings [Abstract]
Short-term borrowings		18,300,000	6,400,000
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount		3,750,300,000	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	300,000	400,000
Unamortized premium (discount) on Senior Notes, net		15,000,000	16,000,000
Deferred gain from termination of interest rate swaps on Senior Notes due 2016		17,700,000	23,100,000
Long-term notes payable, total		3,783,000,000	3,789,500,000
Long-term notes payable, current portion		300,000	400,000
Long-Term Notes Payable		3,782,700,000	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																			18.18	18.249				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																							1,499,792
Convertible Debt, Repurchase Date																								Jun. 17, 2013
Convertible Debt, Repurchase Amount																								600,000
Long-term Debt, Contingent Payment of Principal or Interest																						Beginning August 1, 2013, our Convertible Notes due July 31, 2032 ("2032 Notes") will accrue contingent interest for the six-month period August 1, 2013 to January 31, 2014. Contingent interest of $2.81 per $1,000 principal amount is payable quarterly on October 31, 2013 and January 31, 2014.
Convertible Debt, Contingent Interest Derivative, Interest Expense																					$ 2,800,000