Derivatives Notional Amounts - Designated as Hedges (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 30,963	$ 25,318
Gain (Loss)	(12)	219
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	115,059	174,588
Unrealized Gain (Loss)	73	582
USD / AUD | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	4,050	6,390
Unrealized Gain (Loss)	89	146
USD / CAD | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	2,790	12,221
Unrealized Gain (Loss)	(24)	(101)
USD / CNY | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	2,587	4,460
Unrealized Gain (Loss)	73	32
USD / EUR | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	54,915	70,748
Unrealized Gain (Loss)	406	173
USD / GBP | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	3,224	1,233
Unrealized Gain (Loss)	(109)	0
USD / NZD | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	5,553	10,359
Unrealized Gain (Loss)	140	149
USD / SEK | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	0	603
Unrealized Gain (Loss)	0	0
USD / MXP | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	5,189	7,801
Unrealized Gain (Loss)	155	37
EUR / GBP | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	25,475	41,087
Unrealized Gain (Loss)	(883)	174
EUR / SEK | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	10,252	15,106
Unrealized Gain (Loss)	133	(92)
EUR / NOK | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	0	18
Gain (Loss)	0	0
EUR / NOK | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	0	977
Unrealized Gain (Loss)	0	0
EUR / NZD | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	1,024	2,042
Unrealized Gain (Loss)	93	64
DKK / SEK | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	0	1,561
Unrealized Gain (Loss)	$ 0	$ 0