Accumulated Other Comprehensive Income (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 845,127
Other comprehensive income before reclassifications	(41,535)
Amounts reclassified from OCI	(1,868)
Ending balance	835,741
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(170,062)
Ending balance	(213,465)
Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	164	[1]
Other comprehensive income before reclassifications	(1,094)	[1]
Amounts reclassified from OCI	845	[1]
Ending balance	(85)	[1]
Pension Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,393)	[1]
Other comprehensive income before reclassifications	1,312	[1]
Amounts reclassified from OCI	544	[1]
Ending balance	(2,537)	[1]
Foreign Currency Items [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(165,833)
Other comprehensive income before reclassifications	(41,753)
Amounts reclassified from OCI	(3,257)
Ending balance	$ (210,843)

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