Accumulated Other Comprehensive Income (Loss) by Component - Changes in Accumulated Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (19,335)	$ (9,387)
OCI before reclassifications	55,300	(8,489)
Amount reclassified from accumulated OCI	905	(1,459)
Other Comprehensive Earnings (Loss)	56,205	(9,948)	$ (81,006)
Ending balance	36,870	(19,335)	(9,387)
Foreign Currency
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(26,199)	(5,744)
OCI before reclassifications	76,575	(20,455)
Amount reclassified from accumulated OCI	0	0
Other Comprehensive Earnings (Loss)	76,575	(20,455)
Ending balance	50,376	(26,199)	(5,744)
Long-Term Notes
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	17,372	4,111
OCI before reclassifications	(21,984)	13,261
Amount reclassified from accumulated OCI	0	0
Other Comprehensive Earnings (Loss)	(21,984)	13,261
Ending balance	(4,612)	17,372	4,111
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(11,248)	(9,757)
OCI before reclassifications	3,446	(2,284)
Amount reclassified from accumulated OCI	150	793
Other Comprehensive Earnings (Loss)	3,596	(1,491)
Ending balance	(7,652)	(11,248)	(9,757)
Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	740	2,003
OCI before reclassifications	(2,737)	989
Amount reclassified from accumulated OCI	755	(2,252)
Other Comprehensive Earnings (Loss)	(1,982)	(1,263)
Ending balance	$ (1,242)	$ 740	$ 2,003