Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 852,301
Other comprehensive income (loss) before reclassifications		(14,878)	$ 55,858	$ (41,535)
Amounts reclassified from OCI		46	8,273	(1,868)
Recognition of lease assets and liabilities		(1,389)
Ending balance		859,947	852,301
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(149,334)	(213,465)	(170,062)
Ending balance		(165,555)	(149,334)	(213,465)
Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	(669)	(85)	164
Other comprehensive income (loss) before reclassifications	[1]	667	(768)	(1,094)
Amounts reclassified from OCI	[1]	149	184	845
Recognition of lease assets and liabilities	[1]	0
Ending balance	[1]	147	(669)	(85)
Pension Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	(309)	(2,537)	(4,393)
Other comprehensive income (loss) before reclassifications	[1]	1,130	921	1,312
Amounts reclassified from OCI	[1]	(103)	1,307	544
Recognition of lease assets and liabilities	[1]	(169)
Ending balance	[1]	549	(309)	(2,537)
Foreign Currency Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(148,356)	(210,843)	(165,833)
Other comprehensive income (loss) before reclassifications		(16,675)	55,705	(41,753)
Amounts reclassified from OCI		0	6,782	(3,257)
Recognition of lease assets and liabilities		(1,220)
Ending balance		$ (166,251)	$ (148,356)	$ (210,843)

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