Derivative Instruments (Details) $ in Thousands			1 Months Ended			12 Months Ended
	May 27, 2020 USD ($)	Oct. 03, 2011 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	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]
Amortization of interest expense						$ 1,716	$ 1,355	$ 1,332
Amount to be recognized from hedged transactions within 12 months, approximate						2,500
Additional interest rate contract settlement				$ 4,000
Non-cash interest expense associated with forward starting swaps						$ 6,021	$ 6,327	6,475
Other (Income) Expense Net
Derivative [Line Items]
Foreign currency transaction loss								900
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% Senior Notes, due December 2020 | Senior Notes
Derivative [Line Items]
Interest rate on senior notes						4.50%
Amount to be recognized from hedged transactions within 12 months, approximate	$ (1,400)
4.20% Senior Notes, due December 2021
Derivative [Line Items]
Interest rate on senior notes						4.20%	4.20%			4.20%
4.20% Senior Notes, due December 2021 | Senior Notes
Derivative [Line Items]
Interest rate on senior notes						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 Agreement Settlement on February 28, 2012
Derivative [Line Items]
Notional amount											$ 350,000
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