Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Credit Facilities [Abstract]
Available and unused credit lines	$ 3,657.7	$ 3,437.8
Short-Term Borrowings [Abstract]
Short-term debt	$ 5.2	$ 7.2
Short-term borrowings, weighted average interest rate	3.70%	6.00%
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 4,500.3	$ 4,500.5
Unamortized premium (discount) on senior notes, net	10.1	11.1
Debt issuance costs	(16.9)	(20.5)
Adjustment to carrying value for interest rate swaps	72.1	51.4
Long-term debt, total	4,565.6	4,542.5
Long-term debt, current portion	(1,001.4)	(0.4)
Long-Term Debt	3,564.2	4,542.1
Accumulated other comprehensive income (loss)	(1,015.4)	(618.2)	$ (191.6)
Interest rate swaps, gain on termination	50.4	0.0	0.0
Interest rate swaps, asset, at fair value		42.7
Convertible Debt [Abstract]
Convertible Debt	0.0	0.0
Components of Interest Expense [Abstract]
Interest expense, fees	5.7	6.2	6.5
Interest expense, other	13.7	13.1	14.3
Interest expense, total	181.1	177.2	197.2
Contractual Maturities of Long-Term Debt [Abstract]
Contractual maturities of long-term debt, 2016	1,000.3
Contractual maturities of long-term debt, 2017	0.0
Contractual maturities of long-term debt, 2018	0.0
Contractual maturities of long-term debt, 2019	500.0
Contractual maturities of long-term debt, 2020	1,000.0
Contractual maturities of long-term debt, Thereafter	2,000.0
Contractual maturities of long-term debt	4,500.3
Unrealized Gain (Loss) on Cash Flow Hedge
Long-Term Debt [Abstract]
Accumulated other comprehensive income (loss)	$ (3.3)	0.0	0.0
Cash Flow Hedge [Member]
Long-Term Debt [Abstract]
Interest rate swaps, inception date	Mar. 26, 2015
Interest rate swaps, maturity date	May 02, 2016
Interest rate swaps, notional amount	$ 1,000.0
Interest rate swaps, fixed interest rate	2.32%
Interest rate swaps, liability, at fair value	$ 5.6
Cash Flow Hedge [Member] | Unrealized Gain (Loss) on Cash Flow Hedge
Long-Term Debt [Abstract]
Accumulated other comprehensive income (loss)	(3.3)
Interest Rate Swaps on 2020 Notes [Member]
Long-Term Debt [Abstract]
Interest rate swaps, notional amount		1,000.0
Interest rate swaps, gain on termination	36.9
Interest Rate Swaps on 2022 Notes [Member]
Long-Term Debt [Abstract]
Interest rate swaps, notional amount	1,000.0	1,250.0
Interest rate swaps, gain on termination	13.5
Interest rate swaps, asset, at fair value	$ 32.2
Interest Rate Swaps on 2022 Notes [Member] | LIBOR [Member]
Long-Term Debt [Abstract]
Interest rate swaps, spread	1.05%
Interest Rate Swaps on 2024 Notes [Member]
Long-Term Debt [Abstract]
Interest rate swaps, notional amount	$ 750.0
Interest rate swaps, liability, at fair value	$ 10.0
Interest Rate Swaps on 2024 Notes [Member] | LIBOR [Member]
Long-Term Debt [Abstract]
Interest rate swaps, spread	1.72%
Credit Facility [Member]
Credit Facilities [Abstract]
Credit Facility, maximum borrowing capacity	$ 2,500.0
Credit Facility, expiration date	Jul. 31, 2020
Available and unused credit lines	$ 2,500.0	2,500.0
Credit Facility, covenant terms	The Credit Facility 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 (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 Facility, covenant compliance	At December 31, 2015, we were in compliance with these covenants as our Leverage Ratio was 2.1 times and our Interest Coverage Ratio was 12.2 times.
Commercial Paper [Member]
Credit Facilities [Abstract]
Credit Facility, maximum borrowing capacity	$ 2,000.0
Components of Interest Expense [Abstract]
Interest expense, debt	4.8	2.9	1.7
Uncommitted credit lines [Member]
Credit Facilities [Abstract]
Available and unused credit lines	1,157.7	937.8
Long-Term Debt [Member]
Components of Interest Expense [Abstract]
Interest expense, debt	210.2	192.7	182.0
5.9% Senior Notes due 2016
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 1,000.0	1,000.0
Long-term debt, interest rate	5.90%
Long-term debt, maturity date	Apr. 15, 2016
6.25% Senior Notes due 2019
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 500.0	500.0
Long-term debt, interest rate	6.25%
Long-term debt, maturity date	Jul. 15, 2019
4.45% Senior Notes due 2020
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 1,000.0	1,000.0
Long-term debt, interest rate	4.45%
Long-term debt, maturity date	Aug. 15, 2020
3.625% Senior Notes due 2022
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 1,250.0	1,250.0
Long-term debt, interest rate	3.625%
Long-term debt, maturity date	May 01, 2022
3.65% Senior Notes due 2024
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 750.0	750.0
Long-term debt, interest rate	3.65%
Long-term debt, maturity date	Nov. 01, 2024
Other debt
Long-Term Debt [Abstract]
Long-term debt, carrying amount	$ 0.3	0.5
Interest Rate Swaps [Member]
Components of Interest Expense [Abstract]
Interest expense, debt	$ (53.3)	$ (37.7)	$ (7.3)
Convertible Notes due July 31, 2032
Convertible Debt [Abstract]
Convertible debt, repurchase date		Jul. 31, 2014
Convertible debt, principle amount settled in cash		$ 252.7
Convertible debt, shares issued for conversion premium		1,217,112
2033 Notes and 2038 Notes [Member]
Convertible Debt [Abstract]
Convertible debt, repurchase date		Jun. 17, 2013
Convertible debt, principle amount settled in cash		$ 406.1
Convertible debt, shares issued for conversion premium			1,499,792