Hedging Instruments (Narrative) (Details) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)
Derivative [Line Items]
Estimated net amount of gains expected to be reclassified out of accumulated other comprehensive income and into earnings within next 12 months	$ (5,200)
Discussion of Foreign Currency Derivative Risk Management Policy	We hedge approximately 85 percent of the estimated exposure
Cash Flow Hedge, hedge percentage of Eetimated exposure from intercompany products purchases and sales	85.00%
General duration of foreign currency exchange contracts	24 months
Credit Facility borrowings hedged	$ 80,000
Notional Amount of Foreign Currency Exchange Contracts	176,500	$ 175,900
Unrealized gain (loss) on net investment hedge	$ (8,347)	$ 2,142	$ 1,894
Series C Senior Note [Member]
Derivative [Line Items]
Debt Instrument, Face Amount | €				€ 88.9
Stated interest rate				1.785%
Interest Rate Swap Effective On March 30, 2012 [Member]
Derivative [Line Items]
Fixed portion of interest rate associated with interest rate swap	1.36%
Credit Facility borrowings hedged	$ 40,000
Interest Rate Swap Effective On March 28, 2013 [Member]
Derivative [Line Items]
Fixed portion of interest rate associated with interest rate swap	1.64%
Credit Facility borrowings hedged	$ 40,000