Derivatives and Hedging Activities - Fair Value of Derivative Instruments (Details) € in Millions, $ in Millions	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)	Dec. 31, 2017 USD ($)
Derivatives not designated as hedging instruments:
Total Derivative Assets	$ 2.1		$ 4.1
Total Derivative Liabilities	(3.9)		(5.7)
Net Derivatives	(1.8)		(1.6)
Long-term debt, less current portion	3,242.5		3,230.5
Foreign currency forward contracts
Derivatives not designated as hedging instruments:
Total Derivative Assets	2.1		4.1
Total Derivative Liabilities	(3.9)		(5.7)
Designated as Hedging Instruments | Foreign currency forward contracts
Derivatives not designated as hedging instruments:
Long-term debt, less current portion	462.6	€ 400.0	474.3
Designated as Hedging Instruments | Cash Flow
Derivatives not designated as hedging instruments:
Total Derivative Assets	1.0		0.5
Total Derivative Liabilities	(0.1)		(2.4)
Net Derivatives	0.9		(1.9)
Designated as Hedging Instruments | Cash Flow | Foreign currency forward contracts
Derivatives not designated as hedging instruments:
Total Derivative Assets	1.0		0.5
Total Derivative Liabilities	(0.1)		(2.4)
Non-Designated
Derivatives not designated as hedging instruments:
Total Derivative Assets	1.1		3.6
Total Derivative Liabilities	(3.8)		(3.3)
Net Derivatives	(2.7)		0.3
Non-Designated | Foreign currency forward contracts
Derivatives not designated as hedging instruments:
Total Derivative Assets	1.1		3.6
Total Derivative Liabilities	$ (3.8)		$ (3.3)