Components of Accumulated Other Comprehensive Loss - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax	$ (2,271)	$ 0
Product revenues	447,288	408,038
Interest expense	9,739	9,583
Income from continuing operations before income taxes	27,704	28,295
Income tax expense (benefit)	4,855	8,266
Net income	22,537	19,577
Amount Reclassified from Accumulated Other Comprehensive Loss | Cumulative Unrecognized Actuarial Losses on Pension Obligations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	5,124	5,269
Income tax expense (benefit)	(342)	(325)
Net income	4,782	4,944
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	(19)	59
Income tax expense (benefit)	(44)	(150)
Net income	(63)	(91)
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments | Foreign currency exchange forward contracts
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Product revenues	(32)	(212)
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments | Cross currency interest rate swaps
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	314	271
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments | Interest rate swaps
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(301)	0
Amount Reclassified from Accumulated Other Comprehensive Loss | Actuarial losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit pension income (expense)	5,058	5,142
Amount Reclassified from Accumulated Other Comprehensive Loss | Prior service costs (benefits)
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit pension income (expense)	66	(39)
Amount Reclassified from Accumulated Other Comprehensive Loss | Settlement/curtailment losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined benefit pension income (expense)	$ 0	$ 166