Derivative Instruments - Narrative (Details)	3 Months Ended		9 Months Ended		24 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2011 USD ($) instrument	Dec. 31, 2017 EUR (€)
Derivative [Line Items]
Amortization of interest expense			$ 998,000	$ 989,000
Amount to be recognized from hedged transactions within 12 months, approximate			6,300,000
Other (Income) Expense Net
Derivative [Line Items]
Gain (loss) on derivatives		$ 9,300,000		14,800,000
Foreign currency transaction gain	$ 0
Foreign currency transaction loss	0	$ 10,000,000	900,000	$ 15,200,000
Switzerland
Derivative [Line Items]
Stamp duty expense			2,200,000
4.2% Senior Notes, due December 2021
Derivative [Line Items]
Interest rate on senior notes					4.20%
4.5% Senior Notes, due December 2020
Derivative [Line Items]
Interest rate on senior notes					4.50%
Interest Rate Contract
Derivative [Line Items]
Number of instruments held | instrument					2
Interest Rate Exchange Agreement Expiring 2010 and 2011
Derivative [Line Items]
Amortization of interest expense					$ 68,900,000
Term of amortized interest expense, years					10 years
Foreign currency exchange contracts
Derivative [Line Items]
Derivative, notional amount | €						€ 180,000,000
Cash received from settlement of contracts			6,600,000
Foreign currency exchange contracts | Other (Income) Expense Net
Derivative [Line Items]
Gain (loss) on derivatives	$ 0		$ 900,000