Components of Accumulated Other Comprehensive Loss Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	$ 9,583	$ 11,653
Income from continuing operations before income taxes	28,295	16,767
Income tax expense	8,266	6,253
Net income	19,577	10,137
Amount Reclassified from Accumulated Other Comprehensive Loss | Cumulative Unrecognized Actuarial Losses on Pension Obligations
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	5,269	5,520
Income tax expense	(325)	(522)
Net income	4,944	4,998
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	59	243
Income tax expense	(150)	(94)
Net income	(91)	149
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments | Foreign currency forward exchange contracts
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Revenues	(212)	0
Cost of services and products sold	0	1
Amount Reclassified from Accumulated Other Comprehensive Loss | Effective Portion of Deriviatives Designated as Hedging Instruments | Cross currency interest rate swaps
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	271	242
Amount Reclassified from Accumulated Other Comprehensive Loss | Actuarial losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	5,142	5,467
Amount Reclassified from Accumulated Other Comprehensive Loss | Prior service costs (benefits)
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	(39)	53
Amount Reclassified from Accumulated Other Comprehensive Loss | Settlement/curtailment losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 166	$ 0