Derivative Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	$ 2,198.7	$ 871.7
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	564.9	902.1
Foreign Exchange Contract | Other current assets | Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Asset derivatives	0.7	50.4
Foreign Exchange Contract | Other current assets | Not Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Asset derivatives	1.8	4.0
Foreign Exchange Contract | Investments and other assets | Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Asset derivatives	0.2	6.6
Foreign Exchange Contract | Accrued expenses and other | Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Liability derivatives	84.7
Foreign Exchange Contract | Accrued expenses and other | Not Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Liability derivatives	3.0	9.0
Foreign Exchange Contract | Other long-term liabilities | Designated as Hedging Instrument
Summary of derivatives designated as hedging instruments
Liability derivatives	23.6	4.6
Euro | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	1,875.6	871.7
British pound sterling | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	150.9	0.0
Swiss francs | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	88.7	0.0
Canadian dollar | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Aggregate notional amount	$ 83.5	$ 0.0