Pension and Other Postretirement Benefits (Details 2) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Plan Settlement	$ 0	$ 0	$ (9,856)
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	493,952	461,035
Service cost	6,055	5,395	5,508
Interest cost	18,819	19,494	20,019
Amendments	1,260	2,231
Actuarial loss	23,953	17,475
Benefits paid	29,149	31,188
Transfers in	2,743	25,968
Curtailment gain	(7,030)	0
Plan Settlement	(21,074)	0
Participant contributions	1,355	1,444
Foreign exchange rate changes	7,226	(7,902)
Benefit obligation, ending balance	498,110	493,952	461,035
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	416,912	395,382
Actual return on plan assets	62,281	20,327
Company contributions	14,923	20,101
Participant contributions	1,355	1,444
Benefits paid	(29,149)	(31,188)
Plan Settlements	(20,857)	0
Transfers in	2,743	18,320
Foreign exchange rate changes	6,230	(7,474)
Fair value of plan assets, ending balance	454,438	416,912	395,382
Funded/(underfunded) status, December 31	(43,672)	(77,040)
Pension Plan [Member] \| Domestic Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	389,613	385,629
Service cost	3,931	3,892
Interest cost	17,151	17,523
Amendments	1,233	2,405
Actuarial loss	28,350	6,661
Benefits paid	24,909	26,497
Transfers in	0	0
Curtailment gain	0	0
Plan Settlement	0	0
Participant contributions	0	0
Foreign exchange rate changes	0	0
Benefit obligation, ending balance	415,369	389,613	385,629
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	331,260	326,829
Actual return on plan assets	56,131	13,051
Company contributions	12,896	17,877
Participant contributions	0	0
Benefits paid	(24,909)	(26,497)
Plan Settlements	0	0
Transfers in	0	0
Foreign exchange rate changes	0	0
Fair value of plan assets, ending balance	375,378	331,260	326,829
Funded/(underfunded) status, December 31	(39,991)	(58,353)
Pension Plan [Member] \| Foreign Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	104,339	75,406
Service cost	2,124	1,503
Interest cost	1,668	1,971
Amendments	27	(174)
Actuarial loss	(4,397)	10,814
Benefits paid	4,240	4,691
Transfers in	2,743	25,968
Curtailment gain	(7,030)	0
Plan Settlement	(21,074)	0
Participant contributions	1,355	1,444
Foreign exchange rate changes	7,226	(7,902)
Benefit obligation, ending balance	82,741	104,339	75,406
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	85,652	68,553
Actual return on plan assets	6,150	7,276
Company contributions	2,027	2,224
Participant contributions	1,355	1,444
Benefits paid	(4,240)	(4,691)
Plan Settlements	(20,857)	0
Transfers in	2,743	18,320
Foreign exchange rate changes	6,230	(7,474)
Fair value of plan assets, ending balance	79,060	85,652	68,553
Funded/(underfunded) status, December 31	(3,681)	(18,687)
Other postretirement benefit plans [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, beginning balance	36,853	41,706
Service cost	83	122	145
Interest cost	1,561	1,766	1,836
Actuarial loss	3,806	(3,495)
Benefits paid	7,251	5,621
Participant contributions	2,209	2,281
Foreign exchange rate changes	309	94
Benefit obligation, ending balance	37,570	36,853	41,706
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	0	0
Company contributions	5,042	3,340
Participant contributions	2,209	2,281
Benefits paid	(7,251)	(5,621)
Fair value of plan assets, ending balance	0	0	$ 0
Funded/(underfunded) status, December 31	$ 37,570	$ 36,853

Defined Benefit Plan, Transfers In, Benefit Obligation

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Defined Benefit Plan, Transfers In, Plan Assets

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Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
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Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of (increase) decrease in benefit obligation of defined benefit plan from event reducing expected years of future service of present employees or eliminating accrual of benefits for some or all future services of present employees.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contributions received by defined benefit plan from participant which increases plan assets.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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