Other expense, net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Income and Expenses [Abstract]
Currency transaction losses	$ 690	$ 101
Bank fees	108	149
Components of net periodic pension and postretirement cost other than service	263	622
Other	391	(46)
Total	$ 1,452	$ 826