Consolidated Statements of Comprehensive Income/(Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 32,585	$ 52,812	$ 57,265
Other comprehensive income/(loss), before tax:
Foreign currency translation adjustments	44,162	(23,967)	(51,177)
Pension/postretirement settlements and curtailments		51	103
Pension/postretirement plan remeasurement	2,955	(5,498)	(700)
Amortization of pension liability adjustments:
Prior service credit	(4,453)	(4,450)	(4,440)
Net actuarial loss	5,439	5,102	5,932
Payments related to interest rate swaps included in earnings	1,490	2,400	1,988
Derivative valuation adjustment	325	1,297	(2,961)
Income taxes related to items of other comprehensive income/(loss):
Pension/postretirement settlements and curtailments		(6)
Pension/postretirement plan remeasurement	(918)	1,104	78
Amortization of pension liability adjustments	(22)	27	(270)
Payments related to interest rate swaps included in earnings	(566)	(912)	(755)
Derivative valuation adjustment	(124)	(493)	1,125
Comprehensive income	80,873	27,467	6,188
Comprehensive (loss)/income attributable to the noncontrolling interest	(520)	77	(9)
Comprehensive income attributable to the Company	$ 81,393	$ 27,390	$ 6,197