Derivative Instruments - Narrative (Details) $ in Thousands		1 Months Ended			12 Months Ended
	Oct. 03, 2011 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 09, 2011	Sep. 29, 2011 USD ($)	Jul. 12, 2011 USD ($)	Dec. 06, 2010	Apr. 15, 2010 USD ($)
Derivative [Line Items]
Notional amount										$ 350,000
Amortization of interest expense					$ 1,332	$ 1,320	$ 1,295
Additional interest rate contract settlement			$ 4,000
Expense reclassified into interest expense for interest rate contracts					6,475	6,655	$ 6,851
Amount to be recognized from hedged transactions within 12 months, approximate					6,300
Other (Income) Expense Net
Derivative [Line Items]
Gain on derivatives						19,800
Foreign currency transaction loss					900	$ 20,200
Switzerland
Derivative [Line Items]
Stamp duty expense		$ 2,200
4.50% Senior Notes, due December 2020
Derivative [Line Items]
Interest rate on senior notes						4.50%		4.50%				4.50%
4.20% Senior Notes, due December 2021
Derivative [Line Items]
Interest rate on senior notes						4.20%		4.20%	4.20%
Interest Rate Exchange Agreement Expiring 2010
Derivative [Line Items]
Notional amount													$ 300,000
Interest rate contract settlement amount				$ 31,000
Amortization of interest expense				$ 31,000
Term of amortized interest expense, years			10 years	10 years
Interest rate								5.80%
Interest Rate Exchange Agreement Expiring 2011
Derivative [Line Items]
Notional amount											$ 350,000
Interest rate contract settlement amount	$ 34,700
Interest Rate Exchange Agreements Expiring 2011 And 2012
Derivative [Line Items]
Amortization of interest expense			$ 37,900
Interest rate								5.30%
Settlement amount interest rate contract			38,700
Interest rate settlement recognized as other expense			$ 800
Foreign currency exchange contracts
Derivative [Line Items]
Notional amount | €								€ 180,000,000
Cash received from settlement of contracts					6,600
Foreign currency exchange contracts | Other (Income) Expense Net
Derivative [Line Items]
Gain on derivatives					$ 900