Debt (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014 Rate	Jun. 30, 2014	Dec. 31, 2013
Lines of Credit [Abstract]
Available and unused lines of credit	$ 3,493,300,000	$ 3,493,300,000	$ 3,551,500,000
Short-Term Borrowings [Abstract]
Short-term borrowings	24,700,000	24,700,000	5,900,000
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	3,750,600,000	3,750,600,000	3,750,500,000
Unamortized premium (discount) on Senior Notes, net	14,100,000	14,100,000	14,700,000
Adjustment to carrying value for interest rate swaps	20,900,000	20,900,000	15,900,000
Long-term notes payable, total	3,785,600,000	3,785,600,000	3,781,100,000
Long-term notes payable, current portion	400,000	400,000	400,000
Long-Term Notes Payable	3,785,200,000	3,785,200,000	3,780,700,000
Convertible Debt [Abstract]
Convertible debt, current	252,700,000	252,700,000	0
Convertible Debt	0	0	252,700,000
Credit Agreement expiring October 2016 [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	2,500,000,000	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	2,500,000,000
Credit Agreement, covenant terms		The Credit Agreement contains financial covenants that require us to maintain a Leverage Ratio of consolidated indebtedness to consolidated EBITDA of 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 June 30, 2014, we were in compliance with these covenants, as our Leverage Ratio was 1.9 times and our Interest Coverage Ratio was 11.2 times.
Credit Agreement expiring October 2016 [Member] | Commercial Paper [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	2,000,000,000	2,000,000,000
Uncommitted lines of credit [Member]
Lines of Credit [Abstract]
Available and unused lines of credit	993,300,000	993,300,000	1,051,500,000
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	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	5.90%	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	500,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	6.25%	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	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	4.45%	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	1,250,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	3.625%	3.625%
Maturity date		May 01, 2022
Other notes and loans
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	600,000	600,000	500,000
Convertible Notes due July 31, 2032
Convertible Debt [Abstract]
Convertible debt, total	252,700,000	252,700,000	252,700,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	0.00%	0.00%
Maturity date		Jul. 31, 2032
Convertible Debt, Call Date	Jun. 05, 2014
Convertible Debt, Repurchase Date	Jul. 31, 2014
Convertible Debt, Percentage of Principal Amount Redeemed	100.00%
Convertible Debt, Conversion Rate	18.463
Convertible Debt, Latest Conversion Date	Jul. 29, 2014
Interest Rate Swaps on 2022 Notes [Member]
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest Rate Swaps, Inception Date		May 01, 2014
Interest Rate Swaps, Amount of Hedged Item	$ 1,250,000,000	$ 1,250,000,000