Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 877,724	$ 827,456	$ 859,947	$ 852,301
Other comprehensive income (loss) before reclassifications		2,924	(36,688)	2,357	(12,832)
Amounts reclassified from OCI		(196)	42	(345)	50
Ending balance		897,482	816,429	897,482	816,429
Accumulated Other Comprehensive (Loss) Income [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(166,271)	(125,470)	(165,555)	(149,334)
Ending balance		(163,543)	(162,116)	(163,543)	(162,116)
Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	632	39	147	(669)
Other comprehensive income (loss) before reclassifications	[1]	(531)	(145)	66	525
Amounts reclassified from OCI	[1]	(159)	72	(271)	110
Ending balance	[1]	(58)	(34)	(58)	(34)
Pension Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	512	(339)	549	(309)
Other comprehensive income (loss) before reclassifications	[1]	0	0	0	0
Amounts reclassified from OCI	[1]	(37)	(30)	(74)	(60)
Ending balance	[1]	475	(369)	475	(369)
Foreign Currency Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(167,415)	(125,170)	(166,251)	(148,356)
Other comprehensive income (loss) before reclassifications		3,455	(36,543)	2,291	(13,357)
Amounts reclassified from OCI		0	0	0	0
Ending balance		$ (163,960)	$ (161,713)	$ (163,960)	$ (161,713)

[1] Cash Flow Hedges and Pension Items are net of tax.