Derivatives and Hedging Activities - Fair Value of Derivative Instruments (Detail) € in Millions, $ in Millions	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Derivatives Fair Value [Line Items]
Total Derivative Assets		$ 4.1	$ 40.2
Total Derivative Liabilities		(5.7)	(16.9)
Net Derivatives		(1.6)	23.3
Excludes debt designated as net investment hedge		3,230.5	3,762.6
Foreign Currency Forward Contracts
Derivatives Fair Value [Line Items]
Total Derivative Assets		4.1	16.3
Total Derivative Liabilities		(5.7)	(11.6)
Interest Rate and Currency Swap
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	23.9
Cross-currency swaps
Derivatives Fair Value [Line Items]
Total Derivative Liabilities		0.0	(5.3)
Non-Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Total Derivative Assets		3.6	11.4
Total Derivative Liabilities		(3.3)	(11.5)
Net Derivatives		0.3	(0.1)
Non-Designated as Hedging Instruments | Foreign Currency Forward Contracts
Derivatives Fair Value [Line Items]
Total Derivative Assets		3.6	11.4
Total Derivative Liabilities		(3.3)	(11.5)
Non-Designated as Hedging Instruments | Interest Rate and Currency Swap
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	0.0
Non-Designated as Hedging Instruments | Cross-currency swaps
Derivatives Fair Value [Line Items]
Total Derivative Liabilities		0.0	0.0
Designated as Hedging Instruments | Foreign Currency Forward Contracts
Derivatives Fair Value [Line Items]
Excludes debt designated as net investment hedge	€ 400.0	474.3	416.7
Cash Flow Hedge | Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.5	28.8
Total Derivative Liabilities		(2.4)	(0.1)
Net Derivatives		(1.9)	28.7
Cash Flow Hedge | Designated as Hedging Instruments | Foreign Currency Forward Contracts
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.5	4.9
Total Derivative Liabilities		(2.4)	(0.1)
Cash Flow Hedge | Designated as Hedging Instruments | Interest Rate and Currency Swap
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	23.9
Cash Flow Hedge | Designated as Hedging Instruments | Cross-currency swaps
Derivatives Fair Value [Line Items]
Total Derivative Liabilities		0.0	0.0
Net Investment Hedge | Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	0.0
Total Derivative Liabilities		0.0	(5.3)
Net Derivatives		0.0	(5.3)
Net Investment Hedge | Designated as Hedging Instruments | Foreign Currency Forward Contracts
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	0.0
Total Derivative Liabilities		0.0	0.0
Net Investment Hedge | Designated as Hedging Instruments | Interest Rate and Currency Swap
Derivatives Fair Value [Line Items]
Total Derivative Assets		0.0	0.0
Net Investment Hedge | Designated as Hedging Instruments | Cross-currency swaps
Derivatives Fair Value [Line Items]
Total Derivative Liabilities		$ 0.0	$ (5.3)