Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI(L) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Defined benefit pension, balance January 1	$ (12,320)	$ (9,219)
Foreign currency translation, balance January 1	10,496	15,476
Total, balance January 1	(1,824)	6,257
Other comprehensive income (loss) before reclassifications, defined benefit plan	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	1,206	(4,980)
Total, other comprehensive income (loss) before reclassifications	1,206	(4,980)
Defined benefit pension, amounts reclassified from accumulated other comprehensive income (loss)	(1,336)	(3,101)
Foreign currency translation, amounts reclassified from accumulated other comprehensive income (loss)	0	0
Total, amounts reclassified from accumulated other comprehensive income (loss)	(1,336)	(3,101)
Defined benefit pension, other comprehensive income (loss)	(1,336)	(3,101)	$ (423)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	1,206	(4,980)
Total, other comprehensive income (loss)	(130)	(8,081)
Defined benefit pension, balance December 31	(13,656)	(12,320)	(9,219)
Foreign currency translation, balance December 31	11,702	10,496	15,476
Total, balance December 31	$ (1,954)	$ (1,824)	$ 6,257