Pension and Postretirement Benefits (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) plan	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan expense	$ 17,700	$ 17,200	$ 19,600
Postretirement Medical Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.48%	3.75%	4.25%
Prior service cost to be amortized from accumulated other comprehensive loss next year	$ 100
Estimated net gain (loss) to be amortized from accumulated other comprehensive loss next year	(500)
Company contributions	$ 2,500	$ 4,400	$ 5,100
Assumed rate of increase in medical costs	7.00%	7.50%	7.50%
Minimum medical cost rate to be acheived		5.00%
Domestic Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.63%	4.00%	4.75%
Long-term rate of return on assets	6.00%	6.00%	6.25%
MP Improvement Scale Rate (as a percent)	75.00%
Prior service cost to be amortized from accumulated other comprehensive loss next year	$ 200
Estimated net gain (loss) to be amortized from accumulated other comprehensive loss next year	(5,500)
Company contributions	23,836	$ 22,450
Domestic Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Estimated contributions in the next year	$ 20,000
Domestic Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	48.00%	50.00%
Plan assets, actual allocation (as a percent)	48.00%	51.00%
Domestic Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	52.00%	50.00%
Plan assets, actual allocation (as a percent)	51.00%	49.00%
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.25%	2.34%	3.13%
Long-term rate of return on assets	3.88%	4.68%	5.03%
Prior service cost to be amortized from accumulated other comprehensive loss next year	$ 0
Estimated net gain (loss) to be amortized from accumulated other comprehensive loss next year	(3,700)
Company contributions	18,494	$ 20,004
Estimated contributions in the next year	$ 10,000
Number of plans Non-US Assets | plan	2
Foreign Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	6.00%	11.00%
Plan assets, actual allocation (as a percent)	6.00%	11.00%
Foreign Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	53.00%	45.00%
Plan assets, actual allocation (as a percent)	53.00%	45.00%
Foreign Plan | U.K. , the Netherlands and Canadian Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Plan assets, actual allocation (as a percent)	94.00%