Other expense, net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Other Income and Expenses [Abstract]
Currency transaction (gains)/losses	$ (2,038)	$ 690
Bank fees and amortization of debt issuance costs	109	108
Components of net periodic pension and postretirement cost other than service	281	263
Other	440	391
Total	$ (1,208)	$ 1,452