Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Lines of Credit [Abstract]
Available and unused credit lines	$ 3,437,800,000	$ 3,551,500,000
Short-Term Borrowings [Abstract]
Short-term borrowings	7,200,000	5,900,000
Short-term borrowings, weighted average interest rate	6.00%	5.60%
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	4,500,500,000	3,750,500,000
Unamortized premium (discount) on Senior Notes, net	11,100,000	14,700,000
Adjustment to carrying value for interest rate swaps	51,400,000	15,900,000
Long-term notes payable, total	4,563,000,000	3,781,100,000
Long-term notes payable, current portion	(400,000)	(400,000)
Long-Term Notes Payable	4,562,600,000	3,780,700,000
Long-term notes payable, proceeds from borrowings	747,600,000	0	1,273,200,000
Interest rate swaps, fair value	42,700,000
Convertible Debt [Abstract]
Convertible Debt	0	252,700,000
Components of Interest Expense [Abstract]
Interest expense, fees	6,200,000	6,500,000	6,200,000
Interest expense, other	13,100,000	14,300,000	16,000,000
Interest expense, total	177,200,000	197,200,000	179,700,000
Stated Maturities of Long-Term Notes Payable and Convertible Debt [Abstract]
Stated maturities of long-term notes payable and convertible debt, 2015	400,000
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, 2019	500,000,000
Stated maturities of long-term notes payable and convertible debt, Thereafter	3,000,000,000
Stated maturities of long-term notes payable and convertible debt	4,500,500,000
Interest Rate Swaps on 2022 Notes [Member]
Long-Term Notes Payable [Abstract]
Interest rate swaps, inception date	May 01, 2014
Interest rate swaps, hedged amount	1,250,000,000
Interest Rate Swaps on 2022 Notes [Member] | LIBOR [Member]
Long-Term Notes Payable [Abstract]
Interest rate swaps, spread	1.05%
Interest Rate Swaps on 2020 Notes [Member]
Long-Term Notes Payable [Abstract]
Interest rate swaps, inception date	Sep. 29, 2014
Interest rate swaps, hedged amount	1,000,000,000
Interest Rate Swaps on 2020 Notes [Member] | LIBOR [Member]
Long-Term Notes Payable [Abstract]
Interest rate swaps, spread	2.16%
Credit Agreement expiring July 31, 2019 [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	2,500,000,000
Credit Agreement, expiration date	Jul. 31, 2019
Available and unused credit lines	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 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, 2014 we were in compliance with these covenants, as our Leverage Ratio was 2.0 times and our Interest Coverage Ratio was 12.6 times.
Credit Agreement expiring July 31, 2019 [Member] | Commercial Paper [Member]
Lines of Credit [Abstract]
Credit Agreement, maximum borrowing capacity	2,000,000,000
Commercial Paper [Member]
Components of Interest Expense [Abstract]
Interest expense, debt	2,900,000	1,700,000	1,300,000
Uncommitted lines of credit [Member]
Lines of Credit [Abstract]
Available and unused credit lines	937,800,000	1,051,500,000
Long-Term Notes Payable [Member]
Components of Interest Expense [Abstract]
Interest expense, debt	155,000,000	174,700,000	156,200,000
5.9% Senior Notes due 2016
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,000,000,000	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	5.90%
Maturity date	Apr. 15, 2016
6.25% Senior Notes due 2019
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	500,000,000	500,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	6.25%
Maturity date	Jul. 15, 2019
4.45% Senior Notes due 2020
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,000,000,000	1,000,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	4.45%
Maturity date	Aug. 15, 2020
3.625% Senior Notes due 2022
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	1,250,000,000	1,250,000,000
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	3.625%
Maturity date	May 01, 2022
3.65% Senior Notes due 2024
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	750,000,000	0
Long-Term Notes Payable and Convertible Debt [Abstract]
Interest rate	3.65%
Maturity date	Nov. 01, 2024
Other notes and loans
Long-Term Notes Payable [Abstract]
Long-term notes payable, carrying amount	500,000	500,000
Convertible Notes due July 31, 2032
Convertible Debt [Abstract]
Convertible debt, call date	Jun. 05, 2014
Convertible debt, percentage of principal amount redeemed	100.00%
Convertible debt, conversion rate	18.463
Convertible debt, latest conversion date	Jul. 29, 2014
Convertible debt, shares issued for conversion premium	1,217,112
Convertible debt, repurchase date	Jul. 31, 2014
2033 Notes and 2038 Notes [Member]
Convertible Debt [Abstract]
Convertible debt, call date		May 16, 2013
Convertible debt, percentage of principal amount redeemed		100.00%
Convertible debt, conversion rate		19.4174
Convertible debt, principle amount settled in cash		$ 406,100,000
Convertible debt, shares issued for conversion premium		1,499,792
Convertible debt, repurchase date		Jun. 17, 2013