Derivative Instruments (Details) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended		24 Months Ended
	Apr. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2011 USD ($) instrument	Dec. 31, 2018 EUR (€)
Derivative [Line Items]
Amortization of interest expense			$ 669	$ 664
Amount to be recognized from hedged transactions within 12 months, approximate			$ 6,200
Switzerland
Derivative [Line Items]
Stamp duty expense	$ 2,200
Other (Income) Expense Net
Derivative [Line Items]
Gain (loss) on derivatives		$ (300)		900
Foreign currency transaction gain		$ (300)
Foreign currency transaction loss				900
4.20% Senior Notes, due December 2021
Derivative [Line Items]
Interest rate on senior notes					4.20%
4.50% 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
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