Components of Accumulated Other Comprehensive Loss (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	$ 1,722,380	$ 1,607,062	$ 1,451,223
Interest expense	38,148	47,552	51,584
Total costs and expenses	1,531,453	1,461,668	1,386,340
Income from continuing operations before income taxes	157,254	95,451	(79,471)
Income Tax Expense (Benefit)	12,899	83,803	6,637
Net income (loss)	(145,013)	(11,844)	$ 79,753
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cumulative Unrecognized Actuarial Losses on Pension Obligations
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total costs and expenses	20,124	22,204
Income Tax Expense (Benefit)	(1,389)	(2,093)
Net income (loss)	18,735	20,111
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Actuarial Losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	20,014	21,985
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Prior Service Costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	(139)	219
Reclassification out of Accumulated Other Comprehensive Income [Member] | Settlement/Curtailment Losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	249	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Effective Portion of Derivatives Designated as Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income Tax Expense (Benefit)	(147)	(118)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign currency exchange forward contracts | Effective Portion of Derivatives Designated as Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	(374)	(936)
Cost of services and products sold	0	(18)
Income from continuing operations before income taxes	(218)	48
Net income (loss)	(365)	(70)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cross-currency interest rate swaps | Effective Portion of Derivatives Designated as Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	1,264	1,002
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest rate swaps | Effective Portion of Derivatives Designated as Hedging Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	$ (1,108)	$ 0