Derivative Instruments (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, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2018 EUR (€)	Dec. 09, 2011	Sep. 29, 2011 USD ($)	Jul. 12, 2011 USD ($)	Dec. 06, 2010	Apr. 15, 2010 USD ($)
Derivative [Line Items]
Notional amount										$ 350,000
Amortization of interest expense					$ 1,355	$ 1,332	$ 1,320
Additional interest rate contract settlement			$ 4,000
Non-cash interest expense associated with forward starting swaps					6,327	6,475	6,655
Amount to be recognized from hedged transactions within 12 months, approximate					$ 6,000
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